U.S. patent application number 16/958261 was filed with the patent office on 2020-10-22 for method, device and inspection line for determining the three-dimensional geometry of a container ring surface.
The applicant listed for this patent is TIAMA. Invention is credited to Julien FOUILLOUX, Marc LECONTE.
Application Number | 20200333259 16/958261 |
Document ID | / |
Family ID | 1000004970610 |
Filed Date | 2020-10-22 |
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United States Patent
Application |
20200333259 |
Kind Code |
A1 |
FOUILLOUX; Julien ; et
al. |
October 22, 2020 |
METHOD, DEVICE AND INSPECTION LINE FOR DETERMINING THE
THREE-DIMENSIONAL GEOMETRY OF A CONTAINER RING SURFACE
Abstract
The invention relates to a method, a device and an inspection
line for determining the three-dimensional geometry of a container
ring surface, including the formation, by two optical systems (24,
24'), of two images of the ring surface of the container, according
to two peripheral observation fields having a first and a second
observation elevation angle (.gamma.1, .gamma.2) different from
each other.
Inventors: |
FOUILLOUX; Julien; (LYON,
FR) ; LECONTE; Marc; (LOIRE SUR RHONE, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TIAMA |
VOURLES |
|
FR |
|
|
Family ID: |
1000004970610 |
Appl. No.: |
16/958261 |
Filed: |
December 20, 2018 |
PCT Filed: |
December 20, 2018 |
PCT NO: |
PCT/FR2018/053479 |
371 Date: |
June 26, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 21/9054
20130101 |
International
Class: |
G01N 21/90 20060101
G01N021/90 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 5, 2018 |
FR |
1850105 |
Jan 10, 2018 |
FR |
1850209 |
Claims
1. A method for determining a three-dimensional geometry of an
actual ring surface (16) of a container (14), the ring surface
having a theoretical planar and annular or circular geometry about
a theoretical central axis (A1), of the type including: the
lighting of the actual ring surface (16) of the container, from
above, using a first peripheral incident light beam comprising
first incident radial light rays contained in radial planes
containing the theoretical central axis (A1) and distributed over
360 angle degrees about the installation axis (A'1), said first
incident radial light rays being directed towards the theoretical
central axis (A1), and some of the first incident radial light rays
of the first incident light beam being reflected by specular
reflection on the ring surface (16), in the form of reflected rays
(RR1); the formation, with the reflected rays and via a first
optical system (24, 261), of a first planar optical image of the
ring surface of the container, on a first two-dimensional
photoelectric sensor (18) able to deliver a first overall digital
image; and of the type in which the step consisting in forming a
first planar optical image includes the observation of the ring
surface (16), from above, by a first optical system (24, 261),
according to a first peripheral observation field which observes
the ring surface (16) according to first radial observation rays
which are contained in radial planes containing the theoretical
central axis (A1) and which are distributed at 360 angle degrees
about the theoretical central axis (A1), the first peripheral
observation field having a first observation elevation angle
(.gamma.1) with respect to a plane perpendicular to the theoretical
central axis (A1), so as to collect on the first two-dimensional
photoelectric sensor, in a first annular area of the sensor, rays
reflected to form a first two-dimensional digital image (I161) in a
first image area (ZI1) of the first overall digital image delivered
by the first sensor; characterized in that the method comprises:
the formation, via a second optical system (24', 262), of a second
planar optical image of the ring surface of the container, distinct
from the first planar image, on a second two-dimensional
photoelectric sensor (18, 18') able to deliver a second overall
digital image, by the observation of the ring surface (16), from
above, by the second optical system (24', 262), according to a
second peripheral observation field, symmetrical in rotation about
the theoretical central axis (A1), which observes the ring (16)
according to second radial observation rays which are contained in
radial planes containing the theoretical central axis (A1), which
are distributed at 360 angle degrees about the theoretical central
axis (A1), the second peripheral observation field having a second
observation elevation angle (.gamma.2) with respect to a plane
perpendicular to the theoretical central axis (A1), but different
from the first observation elevation angle (.gamma.1), so as to
collect on the second two-dimensional photoelectric sensor, in a
second annular area of the sensor, reflected rays to form a second
two-dimensional digital image (I162) of the ring surface in a
second image area (ZI2) of the second overall digital image
delivered by the second sensor; and in that the method includes the
determination, for a number N of analyzed directions (Di) derived
from a reference point of the considered digital image and
angularly offset from each other around the reference point: of a
first image point of the first two-dimensional digital image of the
ring surface (16), on the analyzed direction, and of a first value
representative of the distance from this first image point to the
reference point in the first digital image; of a second image point
of the second digital image of the ring surface (16), on the
analyzed direction, and of a value representative of the distance
from this second image point to the reference point in the second
digital image; and in that the method deduces, for the N analyzed
directions, by a geometric relation using the N first values, the N
second values, the first observation elevation angle (.gamma.1),
and the second observation elevation angle (.gamma.2), at least one
value representative of an axial position, along the direction of
the theoretical central axis (A1), of each of the N points of the
actual ring surface (16), whose images by the first optical system
(24) and the second optical system (24') are respectively the N
first image points and the N second image points.
2. The determination method according to claim 1, characterized in
that it includes: the simultaneous observation of the ring surface
(16) by the first optical system (24, 261), according to the first
peripheral observation field, and by the second optical system (24,
262), according to the second peripheral observation field; the
simultaneous formation, from the reflected rays collected according
to the first and second peripheral observation fields, via the
first and second optical systems (24, 261, 262), of the first and
of the second two-dimensional image of the ring surface of the
container simultaneously both in a first image area (ZI1)
corresponding to the observation according to the first peripheral
observation field (.gamma.1) and in a second image area (ZI2)
corresponding to the observation according to the second peripheral
observation field (.gamma.2).
3. The determination method according to claim 1, characterized in
that the first optical system (24) includes a first primary
reflection surface (261) and the second optical system (24', 262)
includes a second primary reflection surface (262), the two primary
reflection surfaces (261, 262) being frustoconical surfaces of
revolution, each generated by a line segment by revolution about
the theoretical central axis (A1), turned towards the theoretical
central axis (A1) and arranged to reflect directly or indirectly
light rays, coming from the actual ring surface under the
corresponding observation elevation angle, in the direction of the
associated sensor.
4. The determination method according to claim 1, characterized in
that the formation of the first and of the second planar optical
image includes for each the optical formation of a complete and
continuous two-dimensional image of the actual ring surface
(16).
5. The determination method according to claim 1, characterized in
that the first peripheral incident light beam includes, in the same
radial plane, non-parallel incident radial light rays. 6. The
determination method according to claim 1, characterized in that
the first incident beam lights the ring surface at an incidence
such that, at the point of reflection of a first incident ray,
whose ray reflected by the actual ring surface (16) is seen by the
first sensor according to the first peripheral observation field,
the normal ("n") to the ring surface (16) forms an angle less than
30 angle degrees with respect to the direction of the theoretical
central axis (A1).
7. The determination method according to claim 1, characterized in
that the second incident beam lights the ring surface at an
incidence such that, at the point of reflection of a second
incident ray, whose ray reflected by the actual ring surface (16)
is seen by the second sensor according to the second peripheral
observation field, the normal ("n") to the ring surface (16) forms
an angle less than 30 angle degrees with respect to the direction
of the theoretical central axis (A1).
8. The determination method according to claim 1, characterized in
that the first observation elevation angle (.gamma.1) is less than
or equal to 45 angle degrees, preferably less than 25 angle
degrees.
9. The determination method according to claim 1, characterized in
that the difference between the two observation elevation angles
(.gamma.1, .gamma.2) is less than or equal to 20 angle degrees.
10. The determination method according to claim 1, characterized in
that the second observation elevation angle (.gamma.2) is greater
than 65 angle degrees, preferably greater than or equal to 75 angle
degrees.
11. The determination method according to claim 1, characterized in
that for the N directions Di, the method deduces, for each
direction, by a geometric triangulation relation using the distance
from the first image point to the reference point in the first
two-dimensional digital image, the distance from the second image
point to the reference point in the second two-dimensional digital
image, the first observation elevation angle (.gamma.1), and the
second observation elevation angle (.gamma.2), at least one value
representative of an axial offset, along the direction of the
theoretical central axis (A1), between the actual ring surface (16)
and a theoretical ring surface.
12. The determination method according to claim 1, characterized in
that for the N directions Di: the first value representative of the
distance from the first image point to the reference point in the
first two-dimensional digital image is the value of a first radial
image offset (dR1i) between a line (I161) representative of the
first image of the ring surface (16) and a theoretical line (I161t)
representative of a theoretical ring surface image in the first
image; the second value representative of the distance from the
second image point to the reference point in the second
two-dimensional digital image is the value of a second radial image
offset (dR2i) between a line (I162) representative of the image of
the ring surface (16) and a theoretical line (I162t) representative
of a theoretical ring surface image in the second image; and in
that the method deduces, for each direction, by a geometric
triangulation relation using the first radial offset, the second
radial offset, the first observation elevation angle (.gamma.1),
and the second observation elevation angle (.gamma.2), at least one
value representative of an axial offset, along the direction of the
theoretical central axis (A1), between the actual ring surface (16)
and a theoretical ring surface.
13. The determination method according to claim 1, characterized in
that a line (I161, I162) representative of the image of the ring
surface is the image, formed by the corresponding optical system
(24) on the associated sensor (18), of the reflection of the
corresponding incident beam on the ring surface (16).
14. The determination method according to claim 1, characterized in
that the first and second two-dimensional photoelectric sensors are
combined into the same two-dimensional photoelectric sensor (18)
delivering a common overall digital image, the first image area
(ZI1) and the second image area (ZI2) being disjoint in the common
overall digital image.
15. A device for determining a three-dimensional geometry of an
actual ring surface (16) of a container (14), the ring surface
having a theoretical planar and annular or circular geometry about
a theoretical central axis (A1), of the type in which the device
(10) has an installation area (E) for a container, this
installation area having an installation axis (A'1), of the type
comprising: a first lighting system (28, 140) having a first light
source (28) which has the installation axis (A'1) as its axis,
which has a diameter greater than the diameter of the ring surface
(16) and which is able to provide a first peripheral incident light
beam comprising first incident radial light rays contained in
radial planes containing the installation axis (A'1) and
distributed over 360 angle degrees about the installation axis
(A'1), said first incident radial light rays being directed towards
the installation axis (A'1); a first two-dimensional photoelectric
sensor (18), connected to an image analysis unit; a first optical
system (24, 261) interposed between the installation area for the
container and the first sensor (18) able to form on the sensor (18)
a first image (I161) of the ring surface (16) of a container (14)
placed in the installation area; of the type in which the first
optical system (24, 261) includes at least a first primary
reflection surface (261) arranged in a downstream portion of the
field-of-view of the first sensor, the first primary reflection
surface (261) being a frustoconical surface of revolution,
generated by a line segment by revolution about the installation
axis (A'1), turned towards the installation axis, and arranged to
reflect, directly or indirectly, in the direction of the first
sensor (18) first light rays coming from the installation area
according to radial planes containing the installation axis (A'1)
and according to a first peripheral observation field having a
first observation elevation angle (.gamma.1) with respect to a
plane perpendicular to the installation axis (A1) thus defining a
first peripheral observation field which observes the ring surface
(16) according to first radial observation rays which are contained
in a radial plane containing the installation axis (A'1), which are
distributed at 360 angle degrees about the theoretical central axis
(A1), and which form with respect to a plane perpendicular to the
installation axis (A'1) the first observation elevation angle; and
of the type in which the first lighting system (28, 140), the first
sensor (18) and the first optical system (24, 261) are arranged
above the installation area; characterized in that the device
includes a second optical system (24, 262), interposed between the
installation area for the container and a second two-dimensional
photoelectric sensor (18), and able to form on the sensor (18) a
second image (I162) of the ring surface (16) of a container (14)
placed in the installation area; in that the second sensor (18) and
the second optical system (24, 262) are arranged above the
installation area; in that the second optical system (24, 262) is
configured to conduct, directly or indirectly, in the direction of
the second sensor (18), second light rays coming from the
installation area according to radial planes containing the
installation axis (A'1) and according to a second peripheral
observation field having a second observation elevation angle
(.gamma.2) with respect to a plane perpendicular to the
installation axis (A'1) thus defining a second peripheral
observation field which observes the ring surface (16) according to
second radial observation rays which are contained in a radial
plane containing the installation axis (A'1), which are distributed
at 360 angle degrees about the theoretical central axis (A1), which
form with respect to a plane perpendicular to the installation axis
(A'1) the second observation elevation angle (.gamma.2), said
second observation elevation angle (.gamma.2) being different from
the first observation elevation angle (.gamma.1); and in that the
first optical system and the second optical system determine for
the first sensor and for the second sensor respectively a first
upstream field-of-view portion and a second upstream field-of-view
portion which overlap in the installation area according to a
useful volume of inspection (VUI) of revolution about the
installation axis (A'1), such that any object point placed in the
useful volume, and illuminated by at least the first light source
so to be imaged by a first image point in the first image formed by
the first optical system on the first sensor, is also imaged by a
second image point in the second image formed by the second optical
system on the second sensor.
16. The device according to claim 15, characterized in that, in the
first upstream field-of-view portion determined by the first
optical system for the first sensor, the first radial observation
rays determined by the first optical system are, when followed from
the useful inspection volume (VUI), centripetal in the direction of
the installation axis, then intersect the installation axis to
become centrifugal in the direction of the first optical system
(24, 261).
17. The device according to claim 15, characterized in that the
device forms two complete, distinct and continuous optical images
(I161, I162) of the actual ring surface (16) on the associated
two-dimensional photoelectric sensor (18).
18. The device according to claim 15, characterized in that the
first primary reflection surface (261) indirectly reflects light
rays in the direction of the sensor (18), and in that the device
includes, between the first primary reflection surface (261) and
the first sensor (18), at least one secondary reflection surface
(132).
19. The device according to claim 15, characterized in that the
second optical system includes at least a second primary reflection
surface (262) in a downstream portion of the field-of-view of the
second sensor (18), the second primary reflection surface being a
frustoconical surface of revolution, generated by a line segment by
revolution about the installation axis, turned towards the
installation axis and arranged to reflect directly or indirectly in
the direction of the sensor (18), light rays, coming from the
installation area according to radial planes containing the
installation axis (A'1) and according to the second peripheral
observation field having the second observation elevation angle
(.gamma.2) with respect to a plane perpendicular to the
installation axis (A'1).
20. The device according to claim 19, characterized in that the
first primary reflection surface (261) and the second primary
reflection surface (262) indirectly reflect light rays in the
direction of the sensor (18), and in that the device includes
between, on the one hand, the first primary reflection surface
(261) and the second primary reflection surface (262) and, on the
other hand, the common sensor (18), at least one secondary
reflection surface (132) of revolution about the installation axis
(A'1).
21. The device according to claim 19, characterized in that the
first primary reflection surface (261) and the second primary
reflection surface (262) each include a frustoconical surface of
revolution, turned towards the installation axis (A'1), having a
small diameter and a large diameter both greater than the largest
diameter of the theoretical ring surface so as to return, in the
direction of the installation axis (A'1), light rays, coming from
the actual ring surface (16) under the corresponding observation
elevation angle (.gamma.1, .gamma.2), said rays then being
intercepted by a send-back reflection surface (132) which includes
a frustoconical surface of revolution (132) turned away from the
installation axis (A'1) so as to return the rays in the direction
of the associated sensor (18).
22. The device according to claim 21, characterized in that the
trajectory of the rays between the two primary reflection surfaces
(261, 262) and the send-back reflection surface (132) is
perpendicular to the installation axis (A'1).
23. The device according to claim 21, characterized in that the
first primary reflection surface (261) and the second primary
reflection surface (262) are each a concave frustoconical surface
and having an apex half-angle (a1, a2) equal to half of the
observation elevation angle (.gamma.1, .gamma.2), and having a
small diameter and a large diameter both greater than the smallest
diameter of the theoretical ring surface.
24. The device according to claim 15, characterized in that the
first observation elevation angle (.gamma.1) is less than or equal
to 45 angle degrees, preferably less than 25 angle degrees.
25. The device according to claim 15, characterized in that the
difference between the two observation elevation angles (.gamma.1,
.gamma.2) is less than 20 angle degrees.
26. The device according to claim 15, characterized in that, in the
second upstream field-of-view portion determined by the second
optical system for the second sensor, the second radial observation
rays determined by the second optical system are, when followed
from the useful inspection volume (VUI), centripetal in the
direction of the installation axis, then intersect the installation
axis to become centrifugal in the direction of the second optical
system (24', 262).
27. The device according to claim 19, characterized in that the
second primary reflection surface (262) directly reflects light
rays in the direction of the second sensor (18), without secondary
reflection surface of revolution.
28. The device according to claim 27, characterized in that, in the
second upstream field-of-view portion determined by the second
optical system for the second sensor, the second radial observation
rays determined by the second optical system are, when followed
from the useful inspection volume (VUI), centrifugal in the
direction of the second primary reflection surface (262).
29. The device according to claim 15, characterized in that, in the
second upstream field-of-view portion determined by the second
optical system for the second sensor, the second radial observation
rays determined by the second optical system are, when followed
from the useful inspection volume (VUI), parallel to the
installation axis or centripetal in the direction of the
installation axis without intersecting the installation axis (A'1)
up to the second optical system.
30. The device according to claim 29, characterized in that the
second optical system is devoid of any reflection surface of
revolution.
31. The device according to claim 15, characterized in that the
second observation elevation angle (.gamma.2) is greater than 65
angle degrees, preferably greater than or equal to 75 angle
degrees.
32. The device according to claim 31, characterized in that the
first observation elevation angle (.gamma.1) is less than or equal
to 45 angle degrees, preferably less than 25 angle degrees.
33. The device according to claim 15, characterized in that the
first optical system includes a telecentric optical system
(20).
34. The device according to claim 15, characterized in that the
second optical system includes a telecentric optical system
(20).
35. The device according to claim 15, characterized in that the
first and second two-dimensional photoelectric sensors are combined
into the same common two-dimensional photoelectric sensor (18), the
first primary reflection surface (261) and the second primary
reflection surface (262) both being in disjoint portions of the
downstream field-of-view of the sensor.
36. The device according to claim 15, characterized in that the
first light source (28) is an annular source of revolution the axis
of which is the installation axis (A'1).
37. A line for inspecting (200) containers (14) having a ring
surface (16), of the type in which containers (14) are moved on a
conveying line by a conveyor (210) which transports the containers
(14) along a horizontal direction of movement perpendicular to a
theoretical central axis (A1) of the containers 14 which thus have
their ring surface (16) in a horizontal plane turned upwards,
characterized in that the installation includes a device (10)
according to claim 15, which is arranged on the installation with
its installation axis (A'1) in a vertical position, such that the
observation fields and the incident light beams are arranged
downwards, towards the installation area (E) which is located
between the device and a transport member of the conveyor
(212).
38. The inspection line (200) according to claim 37, characterized
in that the conveyor (210) brings the containers such that their
theoretical central axis (A1) coincides with the installation axis
(A'1) and, at the time of this coincidence, at least one image is
acquired thanks to the device (10), without contact of the device
(10) with the container (14).
Description
[0001] The invention relates to the field of the inspection of the
containers, in particular containers made of glass, and more
specifically the control of the evenness of the ring surface of
such containers.
[0002] The ring surface is the upper surface or the upper ridge of
the ring of the container. Of annular shape about a theoretical
central axis of the ring, the ring surface is more or less thick
along a direction radial to the theoretical central axis. In
theory, this surface is planar in a plane perpendicular to the
theoretical central axis, in the sense that it has at least one
continuous contact line on 360 angle degrees about the axis with
this plane, and it is perfectly circular. While being planar in the
sense above, its profile in sections through a radial plane
containing the theoretical central axis can have different shapes:
the profile can be flat, rounded, inverted V-shaped, etc.
[0003] In many applications, the ring surface is the one that is
intended to come into contact with the seal of the cover or of the
cap. When the ring surface is not planar, leaks will be possible
after closure. It is therefore important to know the unevenness of
the ring surface. This unevenness can be analyzed, at a given point
of the ring surface, as a height difference understood in this text
as a position difference, along a direction parallel to the
theoretical central axis of the ring of the container, between a
given point of the actual ring surface of the container and the
corresponding point of a theoretical ring surface. These two points
are matching in that, in a system of cylindrical coordinates,
centered on the theoretical central axis, the corresponding points
have the same angular coordinate, and belong, for the one to the
actual ring surface, and for the other to the theoretical ring
surface. This theoretical surface is therefore planar with respect
to a reference plane perpendicular to the theoretical central axis.
This reference plane can be linked to the considered container, and
can for example correspond to the height of the highest point of
the actual ring surface, to the height of the lowest point of the
actual ring surface, to an average height of the ring surface over
its angular extent, etc. The reference plane can also be defined
independently of the container, with reference for example to a
viewing, control or measurement device.
[0004] The unevenness of the ring surface is often distinguished
into at least two types. Defects of the "dip"-type are linked to
problems of filling the ring mold with the molten glass during
manufacture. They are characterized by height deviations which
extend over small angular amplitude about the theoretical central
axis. Defects of the "saddle"-type are generally less marked height
deviations, which extend over greater angular amplitude about the
theoretical central axis, but are nevertheless inconvenient
defects, often due to sagging, to problems during the extraction of
the articles from the mold, or to thermal problems during the
manufacture.
[0005] The ring surface may have other geometry defects. It can for
example have a characteristic plane inclined with respect to the
body of the article or with respect to the bottom of the article. A
characteristic plane of the ring surface can be a mid-plane, or a
geometric plane based on the ring. It is considered that the ring
is inclined if this characteristic plane is not parallel to the
plane for laying the article, or not orthogonal to the axis of
symmetry of the article, with an angle greater than a given
threshold.
[0006] The ring surface, and generally the entire ring, may have a
defect in the roundness, for example an ovalization, that is to say
the ring surface seen from above, or the planar section of the ring
by a horizontal plane, is neither a circle nor an annulus. For
example, the shape is that of an oval or the shape may have a
crushing.
[0007] Currently, the unevenness is detected mainly by a system
called "bell" system by detection of gas leaks. The residual leak
is measured when a planar metal surface is pressed on the ring. The
disadvantage is that the control does not give any element that
allows assessing the extent of the defect, but only allows
obtaining a binary indication (leak/no leak) indicative of the
evenness or unevenness of the surface. Such a system requires
mechanical means for relatively moving the container relative to
the device, which are not only costly but which also slow down the
rate of the inspection line: raising and lowering of the bell,
temporary immobilization of the article under the bell, etc. In
addition, there is an actual interest in removing any contact with
the ring of the article to avoid risks of breakage or
pollution.
[0008] According to the patent U.S. Pat. No. 6,903,814 B1, it is
planned to measure the height of the ring in 4 points disposed at
90 angle degrees, by means of 4 laser triangulation distance
sensors, adapted to the specular reflection. The article is rotated
and the position of a point with respect to the plane passing
through the 3 other ones is compared at each increment of rotation.
Several calculation alternatives are possible, but the disadvantage
of the system are on the one hand the costly use of handling
equipment for the rotation and on the other hand the difficulty of
completely separating the effects of the rotational defects from
the effects of unevenness, in spite of convolution
calculations.
[0009] Vision systems are also known in which the rings are
observed according to at least two views from a high angle or a low
angle. A diffuse lighting located opposite the cameras relative to
the articles lights the article to be controlled in transmission.
The disadvantage of this system is that it requires at least two
cameras and two light sources and possibly two telecentric optics
and their supports and settings. The assembly is costly, and
requires long optical paths, which results in a significant
bulk.
[0010] To overcome these disadvantages, it has been proposed to
use, as disclosed above, cameras already provided for carrying out
another control of the container, for example, in the case of
transparent glass bottles, a control of aspect in the shoulder.
However, this requires choosing positions for the control device
which can only be a compromise between the settings for detecting
the defects in the shoulder area and the settings for detecting the
geometric defects in the ring surface. These compromises are not
satisfactory either for the measurement initially targeted by these
cameras, or for the measurement of evenness desired to be made
thereby.
[0011] By multiplying the angles of view, in particular by
combining similar views under different high or low angles, it is
also possible to measure in 3D portions of the ring and then to
collect these measurements to reconstruct by calculation the total
geometry of the ring surface It uses the acquisition of several
optical images. These optical images are then combined two by two
by algorithms for matching points in pairs, from which actual
points in 3D coordinates are calculated by triangulation. The
technique is that of the stereovision with complex algorithms.
Several pairs of stereovision views are necessary, which therefore
requires for example 4 or 6 cameras. These systems can be accurate,
but they are very costly and very bulky. Due to the numerous
parameters, the accuracy is not kept in operation for a long
time.
[0012] Document U.S. Pat. No. 6,172,748 describes a device
including several distinct light sources which light the ring from
below, that is to say from a point located below a plane
perpendicular to the axis of the ring and tangent to the ring
surface. The device includes several distinct mirrors which each
provide an image of only one angular sector of the ring. An
additional camera makes a top view of the ring surface. Even if the
lateral images overlap, there is an azimuthal angular discontinuity
between the images because, at a possible point of overlapping of
the two images, there is a point breakage seen between the
overlapping points in each of the images. This makes a computer
reconstruction of the image necessary, which requires complex
algorithms jeopardizing the measurement accuracy.
[0013] Document WO-2016/059343 of the applicant describes an
innovative method for viewing the evenness of a ring surface, and
an associated device. The methods and devices described in this
document are particularly relevant but can be sensitive in
particular to the off-centering or to an uncontrolled inclination
of the ring surface.
[0014] Document WO-2008/050067 of the applicant describes a device
that allows observing an area to be inspected of a container from
several different viewing angles.
[0015] An objective of the invention is therefore to propose a
method and device for determining the three-dimensional geometry of
a ring surface, in particular with a view to determining the
presence of possible unevenness which remain simple to implement
but whose results are less influenced by an off-centering or an
uncontrolled inclination of the ring surface with respect to the
installation axis.
[0016] Also, the invention proposes in particular a method for
determining a three-dimensional geometry of an actual ring surface
of a container, the ring surface having a theoretical planar and
annular or circular geometry about a theoretical central axis, of
the type including: [0017] the lighting of the actual ring surface
of the container, from above, using a first peripheral incident
light beam comprising first incident radial light rays contained in
radial planes containing the theoretical central axis and
distributed at 360 angle degrees about the installation axis, said
first incident radial light rays being directed towards the
theoretical central axis, and some of the first incident radial
light rays of the first incident light beam being reflected by
specular reflection on the ring surface, in the form of reflected
rays; [0018] the formation, with the reflected rays and via a first
optical system, of a first planar optical image of the ring surface
of the container, on a first two-dimensional photoelectric sensor
able to deliver a first overall digital image; [0019] and of the
type in which the step consisting in forming a first planar optical
image includes the observation of the ring surface, from above, by
a first optical system, according to a first peripheral observation
field which observes the ring surface according to first radial
observation rays which are contained in radial planes containing
the theoretical central axis and which are distributed at 360 angle
degrees about the theoretical central axis, the first peripheral
observation field having a first observation elevation angle, which
in some cases will be less than or equal to 45 angle degrees,
sometimes less than 25 angle degrees, with respect to a plane
perpendicular to the theoretical central axis, so as to collect on
the first two-dimensional photoelectric sensor, in a first annular
area of the sensor, rays reflected to form a first two-dimensional
digital image in a first image area of the first overall digital
image delivered by the first sensor.
[0020] The method is characterized in that it comprises: [0021] the
formation, via a second optical system, of a second planar optical
image of the ring surface of the container, distinct from the first
planar image, on a second two-dimensional photoelectric sensor able
to deliver a second overall digital image, by the observation of
the ring surface, from above, by the second optical system,
according to a second peripheral observation field, symmetrical in
rotation about the theoretical central axis, which observes the
ring according to second radial observation rays which are
contained in radial planes containing the theoretical central axis,
which are distributed at 360 angle degrees about the theoretical
central axis, the second peripheral observation field having a
second observation elevation angle with respect to a plane
perpendicular to the theoretical central axis, but different from
the first observation elevation angle, so as to collect on the
second two-dimensional photoelectric sensor, in a second annular
area of the sensor, reflected rays to form a second two-dimensional
digital image of the ring surface in a second image area of the
second overall digital image delivered by the second sensor; [0022]
and in that the method includes the determination, for a number N
of analyzed directions derived from a reference point of the
considered digital image and angularly offset from each other
around the reference point: [0023] of a first image point of the
first two-dimensional digital image of the ring surface, on the
analyzed direction, and of a first value representative of the
distance from this first image point to the reference point in the
first digital image; [0024] of a second image point of the second
digital image of the ring surface, on the analyzed direction, and
of a value representative of the distance from this second image
point to the reference point in the second digital image; [0025]
and in that the method deduces, for the N analyzed directions, by a
geometric relation using the N first values, the N second values,
the first observation elevation angle, and the second observation
elevation angle, at least one value representative of an axial
position, along the direction of the theoretical central axis, of
each of the N points of the actual ring surface, whose images by
the first optical system and the second optical system are
respectively the N first image points and the N second image
points.
[0026] According to other optional characteristics of the method,
taken alone or in combination: [0027] The method may include:
[0028] the simultaneous observation of the ring surface by the
first optical system, according to the first peripheral observation
field, and by the second optical system, according to the second
peripheral observation field; [0029] the simultaneous formation,
from the reflected rays collected according to the first and second
peripheral observation fields, via the first and second optical
systems, of the first and of the second two-dimensional image of
the ring surface of the container simultaneously both in a first
image area corresponding to the observation according to the first
peripheral observation field and in a second image area
corresponding to the observation according to the second peripheral
observation field. [0030] The first optical system may include a
first primary reflection surface and the second optical system may
include a second primary reflection surface, the two primary
reflection surfaces being frustoconical surfaces of revolution,
each generated by a line segment by revolution about the
theoretical central axis, turned towards the theoretical central
axis and arranged to reflect directly or indirectly light rays,
coming from the actual ring surface under the corresponding
observation elevation angle, in the direction of the associated
sensor. [0031] The formation of the first and of the second planar
optical image can include for each the optical formation of a
complete and continuous two-dimensional image of the actual ring
surface. [0032] The first peripheral incident light beam may
include, in the same radial plane, non-parallel incident radial
light rays. [0033] The first incident beam can light the ring
surface at an incidence such that, at the point of reflection of a
first incident ray, whose ray reflected by the actual ring surface
is seen by the first sensor according to the first peripheral
observation field, the normal to the ring surface forms an angle
less than 30 angle degrees with respect to the direction of the
theoretical central axis. [0034] The second incident beam can light
the ring surface at an incidence such that, at the point of
reflection of a second incident ray, whose ray reflected by the
actual ring surface is seen by the second sensor according to a
second peripheral observation field, the normal to the ring surface
forms an angle less than 30 angle degrees with respect to the
direction of the theoretical central axis. [0035] The difference
between the two observation elevation angles may be less than or
equal to 20 angle degrees. [0036] As an alternative, the second
observation elevation angle can be greater than 65 angle degrees,
or even greater than or equal to 75 angle degrees. [0037] For the N
directions Di, the method can deduce, for each direction, by a
geometric triangulation relation using the distance from the first
image point to the reference point in the first two-dimensional
digital image, the distance from the second image point to the
reference point in the second two-dimensional digital image, the
first observation elevation angle, and the second observation
elevation angle, at least one value representative of an axial
offset, along the direction of the theoretical central axis,
between the actual ring surface and a theoretical ring surface.
[0038] For the N directions Di: [0039] the first value
representative of the distance from the first image point to the
reference point in the first two-dimensional digital image may be
the value of a first radial image offset between a line
representative of the first image of the ring surface and a
theoretical line representative a theoretical ring surface image in
the first image; [0040] the second value representative of the
distance from the second image point to the reference point in the
second two-dimensional digital image can be the value of a second
radial image offset between a line representative of the image of
the ring surface and a theoretical line representative of a
theoretical ring surface image in the second image; [0041] and the
method can deduce, for each direction, by a geometric triangulation
relation using the first radial offset, the second radial offset,
the first observation elevation angle, and the second observation
elevation angle, at least one value representative of an axial
offset, along the direction of the theoretical central axis,
between the actual ring surface and a theoretical ring surface.
[0042] The line representative of the image of the ring surface can
be the image, formed by the corresponding optical system on the
associated sensor, of the reflection of the corresponding incident
beam on the ring surface. [0043] The first and second
two-dimensional photoelectric sensors can be combined into the same
two-dimensional photoelectric sensor delivering a common overall
digital image, the first image area and the second image area being
disjoint in the common overall digital image.
[0044] The invention also relates to a device for determining a
three-dimensional geometry of an actual ring surface of a
container, the ring surface having a theoretical planar and annular
or circular geometry about a theoretical central axis, of the type
in which the device has an installation area for a container, this
installation area having an installation axis, of the type
comprising: [0045] a first lighting system having a first light
source which has the installation axis as its axis, which has a
diameter greater than the diameter of the ring surface and which is
able to provide a first peripheral incident light beam comprising
first incident radial light rays contained in radial planes
containing the installation axis and distributed at 360 angle
degrees about the installation axis, said first incident radial
light rays being directed towards the installation axis; [0046] a
first two-dimensional photoelectric sensor, connected to an image
analysis unit; [0047] a first optical system interposed between the
installation area for the container and the first sensor able to
form on the sensor a first image of the ring surface of a container
placed in the installation area;
[0048] of the type in which the first optical system includes at
least a first primary reflection surface arranged in a downstream
portion of the field-of-view of the first sensor, the first primary
reflection surface being a frustoconical surface of revolution,
generated by a line segment by revolution about the installation
axis, turned towards the installation axis, and arranged to
reflect, directly or indirectly, in the direction of the first
sensor of the first light rays coming from the installation area
according to radial planes containing the installation axis and
according to a first peripheral observation field having a first
observation elevation angle with respect to a plane perpendicular
to the installation axis thus defining a first peripheral
observation field which observes the ring surface according to
first radial observation rays which are contained in a radial plane
containing the installation axis, which are distributed at 360
angle degrees about the theoretical central axis, and which form
with respect to a plane perpendicular to the installation axis the
first observation elevation angle, which will be in some cases less
than or equal to 45 angle degrees, sometimes less than 25
degrees;
[0049] and of the type in which the first lighting system, the
first sensor and the first optical system are arranged above the
installation area;
[0050] characterized in that [0051] the device includes a second
optical system, interposed between the installation area for the
container and a second two-dimensional photoelectric sensor, and
able to form on the sensor a second image of the ring surface of a
container placed in the installation area; [0052] in that the
second sensor and the second optical system are arranged above the
installation area; [0053] in that the second optical system is
configured to conduct, directly or indirectly, in the direction of
the second sensor, second light rays coming from the installation
area according to radial planes containing the installation axis
and according to a second peripheral observation field having a
second observation elevation angle with respect to a plane
perpendicular to the installation axis thus defining a second
peripheral observation field which observes the ring surface
according to second radial observation rays which are contained in
a radial plane containing the installation axis, which are
distributed at 360 angle degrees about the theoretical central
axis, and which form with respect to a plane perpendicular to the
installation axis the second observation elevation angle, said
second observation elevation angle being different from the first
observation elevation angle; [0054] and in that the first optical
system and the second optical system determine for the first sensor
and for the second sensor respectively a first upstream
field-of-view portion and a second upstream field-of-view portion
which overlap in the installation area according to a useful volume
of inspection of revolution about the installation axis, such that
any object point placed in the useful volume, and illuminated by at
least the first light source so as to be imaged by a first image
point in the first image formed by the first optical system on the
first sensor, is also imaged by a second image point in the second
image formed by the second optical system on the second sensor.
[0055] According to other optional characteristics of the device,
taken alone or in combination: [0056] In the first upstream
field-of-view portion determined by the first optical system for
the first sensor, the first radial observation rays determined by
the first optical system can be, when followed from the useful
inspection volume, centripetal in the direction of the installation
axis, then can intersect the installation axis to become
centrifugal in the direction of the first optical system. [0057]
The device can form two complete, distinct and continuous optical
images of the actual ring surface on the associated two-dimensional
photoelectric sensor. [0058] The first primary reflection surface
can indirectly reflect light rays in the direction of the sensor,
and the device can include, between the first primary reflection
surface and the first sensor, at least one secondary reflection
surface. [0059] The second optical system may include at least a
second primary reflection surface in a downstream portion of the
field-of-view of the second sensor, the second primary reflection
surface being a frustoconical surface of revolution, generated by a
line segment by revolution about the installation axis, turned
towards the installation axis and arranged to reflect directly or
indirectly in the direction of the sensor, light rays, coming from
the installation area according to radial planes containing the
installation axis and according to the second peripheral
observation field having the second observation elevation angle
with respect to a plane perpendicular to the installation axis.
[0060] The first primary reflection surface and the second primary
reflection surface can indirectly reflect light rays in the
direction of the sensor, and the device can include between, on the
one hand, the first primary reflection surface and the second
primary reflection surface and, on the other hand, the common
sensor, at least a secondary reflection surface of revolution about
the installation axis. [0061] The first primary reflection surface
and the second primary reflection surface may each include a
frustoconical surface of revolution, turned towards the
installation axis, having a small diameter and a large diameter
both greater than the largest diameter of the theoretical ring
surface so as to return, in the direction of the installation axis,
light rays, coming from the actual ring surface under the
corresponding observation elevation angle, said rays being
intercepted by a send-back reflection surface which includes a
frustoconical surface of revolution turned away from the
installation axis so as to return the rays in the direction of the
associated sensor. [0062] The trajectory of the rays between the
two primary reflection surfaces and the send-back reflection
surface can be perpendicular to the installation axis. [0063] The
first primary reflection surface and the second primary reflection
surface may each be a concave frustoconical surface and having an
apex half-angle equal to half of the observation elevation angle,
and having a small diameter and a large diameter both greater than
the smallest diameter of the theoretical ring surface. [0064] The
difference between the two observation elevation angles can be less
than 20 angle degrees. [0065] The second upstream field-of-view
portion determined by the second optical system for the second
sensor, the second radial observation rays determined by the second
optical system are, when followed from the useful inspection
volume, centripetal in the direction of the installation axis, then
intersect the installation axis to become centrifugal in the
direction of the second optical system. [0066] The second primary
reflection surface can directly reflect light rays in the direction
of the second sensor, without a secondary reflection surface of
revolution. [0067] In the second upstream field-of-view portion
determined by the second optical system for the second sensor, the
second radial observation rays determined by the second optical
system can be, when followed from the useful inspection volume,
centrifugal in the direction of the second primary reflection
surface. [0068] In the second upstream field-of-view portion
determined by the second optical system for the second sensor, the
second radial observation rays determined by the second optical
system can be, when followed from the useful inspection volume,
parallel to the installation axis or centripetal in the direction
of the installation axis without intersecting the installation axis
so as to move away from the installation axis when followed from
the useful inspection volume towards the second optical system.
[0069] The second optical system can be devoid of any reflection
surface of revolution. [0070] The second observation elevation
angle may be greater than 65 angle degrees, preferably greater than
or equal to 75 angle degrees. [0071] The first optical system may
include a telecentric optical system. [0072] The second optical
system may include a telecentric optical system. [0073] The first
and second two-dimensional photoelectric sensors can be combined
into the same common two-dimensional photoelectric sensor, the
first primary reflection surface and the second primary reflection
surface are both in disjoint portions of the downstream
field-of-view of the sensor. [0074] The first light source can be
an annular source of revolution the axis of which is the
installation axis.
[0075] The invention also relates to a line for inspecting
containers having a ring surface, of the type in which containers
are moved on a conveying line by a conveyor which transports the
containers along a horizontal direction of movement perpendicular
to a theoretical central axis of the containers which thus have
their ring surface in a horizontal plane turned upwards,
characterized in that the installation includes a device having any
one of the characteristics above, which is arranged on the
installation with its installation axis in a vertical position,
such that the observation fields and the incident light beams are
arranged downwards, towards the installation area which is located
between the device and a transport member of the conveyor.
[0076] In such an inspection line, the conveyor can bring the
containers such that their theoretical central axis coincides with
the installation axis and, at the time of this coincidence, at
least one image can be acquired thanks to the device, without
contact of the device with the container.
[0077] Various other characteristics will emerge from the
description given below with reference to the appended drawings
which show, by way of non-limiting examples, embodiments of the
object of the invention.
[0078] FIG. 1A is an axial sectional view of a first embodiment of
a device according to the invention.
[0079] FIG. 1B is a perspective diagram of some elements of the
first embodiment of FIG. 1A.
[0080] FIG. 1C is an enlarged axial sectional diagram illustrating
the fields-of-view for the first embodiment of FIG. 1A.
[0081] FIG. 1D is a diagram of an image obtained with the device of
FIG. 1A.
[0082] FIG. 2 is an enlarged axial sectional diagram illustrating a
variant of embodiment of a lighting system.
[0083] FIGS. 3, 4 and 5 are views similar to that FIG. 1
illustrating other embodiments of a device according to the
invention.
[0084] FIG. 6 illustrates an inspection line according to the
invention.
[0085] FIGS. 7A and 7B are views which illustrate variants of the
invention in which none of the two observation elevation angles is
less than 25 angle degrees. In the example of FIG. 7A, the first
observation elevation angle is less than or equal to 45 angle
degrees and the second observation elevation angle is greater than
45 angle degrees. In the example of FIG. 7B, the first and second
observation elevation angles are both greater than 45 angle
degrees.
[0086] FIGS. 1A, 3, 4, 5, 7A, and 7B illustrate, in sections
through a radial plane Pri as illustrated in FIG. 1B, different
embodiments of a device for determining the three-dimensional
geometry of an actual ring surface of a container, each of these
devices allowing the implementation of a method according to the
invention. The figures illustrate only the upper part of the ring
12 of a container 14. A container 14 is defined as a hollow vessel
defining an interior volume which is closed over its entire volume
periphery except at an upper ring 12 open at one end.
[0087] For convenience, and only by way of arbitrary definition, it
will indeed be considered that the container includes a theoretical
central axis A1, defined as being the theoretical central axis of
its ring 12. It will also be arbitrarily considered that the ring
is arranged at the upper end of the container. Thus, in the present
text, the notions of high, low, upper and lower have a relative
value corresponding to the orientation of the device 10 and of the
container 14 as represented in the figures. However, it is
understood that the invention could be implemented with an absolute
orientation indifferent in space, insofar as the different
components remain arranged with the same relative arrangement.
[0088] The ring 12 of the container is cylindrical of revolution
about the axis A1. The body of the container, not represented, also
may or may not be a volume of revolution. The ring 12 is connected
through its lower end (not represented) to the rest of the body of
the container, while its other free end, called upper end by
arbitrary choice within the context of the present description,
terminates in a ring surface 16.
[0089] The ring surface 16 is theoretically planar and parallel to
a plane perpendicular to the axis A1, in the sense that it has at
least one continuous contact line at 360 angle degrees about the
theoretical central axis with such a plane, and it is theoretically
circular or annular in this plane. In the present text, the actual
ring surface of the container, on the one hand, and a theoretical
ring surface, on the other hand, will be distinguished. This
theoretical ring surface is therefore a planar surface or a planar
circle in a reference plane perpendicular to the theoretical
central axis A1. This reference plane can be defined as linked to
the considered container, such as the reference plane PRef in FIG.
1A which is tangent to a point of the actual ring surface 16, for
example the highest point along the direction of the theoretical
central axis A1. Alternatively, this reference plane can for
example be located at the height of the lowest point of the actual
ring surface, at an average height of the ring surface over its
angular extent, etc. The reference plane can also be defined
independently of the container, with reference for example to one
of the elements of the device 10, for example at a lower surface of
a casing of the device 10. The reference plane can thus be a
reference plane of the installation P'ref perpendicular to an
installation axis as defined below.
[0090] The determination of the three-dimensional geometry of the
ring surface can for example comprise the quantification of a
position deviation, along the direction of the theoretical central
axis A1, between a given point Ti of the actual ring surface and a
corresponding point Tti of the theoretical ring surface. These two
points are matching in that, in a system of cylindrical
coordinates, centered on the theoretical central axis, the
corresponding points Ti, Tti have the same angular coordinate, and
belong, for the one to the actual ring surface and, for the other,
to the theoretical ring surface. In other words, they are arranged
in the same radial plane Pri containing the theoretical central
axis A1.
[0091] In the illustrated examples, the ring surface 16 has, in
sections through a radial plane containing the theoretical central
axis, a bulged, convex radial profile between an inner edge and an
outer edge. The inner edge can be considered as being at the
intersection of the ring surface 16 and of an inner surface of the
ring of the container, whose general orientation is close to that
of the axis A1 of the container 14. However the profile of the ring
surface 16, in sections through radial planes containing the
theoretical central axis, could have a different shape: the profile
can be flat, rounded, inverted V-shaped, etc.
[0092] To ensure a proper inspection of the container, it will be
important to make sure that the container is presented
appropriately in front of the device 10. For this, the device 10
according to the invention includes an installation area E in which
the container must be installed. This installation area can be
defined by an installation axis A'1 and an installation plane (not
represented) defined as being a plane perpendicular to the
installation axis A'1 located at the lowest point of the device.
Thus, in order to be properly inspected, a container will be
preferably presented so that its theoretical central axis A1 is at
best parallel to the installation axis A'1, in particular if its
laying plane is parallel to the installation plane. Thus, to be
properly inspected, a container will also be preferably presented
so that its theoretical central axis A1. corresponds at best to the
installation axis A'1, and that its ring is presented with its open
upper end turned in the direction of the device 10, but below the
installation plane. In an ideal case, which will form the
hypothesis of the explanations below, the two axes A1 and A'1 are
coincident. However, with the invention, it will be seen that a
possible shift, between the two axes A1 and A'1 (in the sense of a
transverse deviation along a direction perpendicular to these axes
A1 and A'1, and/or of an angular deviation between the two axes A1
and A'1) will be compensated by the invention and will not
significantly affect the determination of the axial position of a
point of the ring surface 16. It is understood that the entire
device 10 according to the invention can be positioned above the
installation plane while the container will be brought below the
installation plane, without risk of contact with the device. The
container 14 can therefore be brought into the installation area E
by any motion, preferably in translation on a straight or
non-straight trajectory, along a direction perpendicular to the
installation axis without risk of interference with the device
10.
[0093] The device and the method according to the invention make
use of at least one two-dimensional photoelectric sensor 18
intended to acquire a two-dimensional image of the actual ring
surface of the container or, in some embodiments, two of such
sensors 18, 18'. Such a sensor, also qualified as a matrix sensor,
can be incorporated into a camera 19, 19' and can for example be of
the CCD or CMOS type. Such a sensor 18, 18' is for example made up
of a two-dimensional matrix of photoelectric elements. The sensor
is generally associated with an electronic circuit for processing
the signals provided by the photoelectric elements to deliver an
analog or digital signal representative of the image received by
the sensor. This signal representative of the optical image
received by the sensor preferably constitutes an electronic,
digital, two-dimensional image, which can then be delivered to an
image processing device and/or to a viewing device and/or to an
image storage device (not represented).
[0094] Such a sensor 18,18' is generally associated with an optical
lens system 20, 20' which may include one or more optical elements,
in particular one or more thin lens(es), and possibly a diaphragm,
associated to allow the formation of an optical image of the
installation area on the sensor. The optical lens system 20, 20',
or at least a part thereof, and the sensor 18, 18' are generally
part of the camera 19, 19'.
[0095] By "optical system" is meant according to the invention an
observation system into which light rays coming from a lighted
object enter to form a planar image.
[0096] According to the invention, it is considered that two
optical systems 24, 24' are interposed optically, i.e. both in
parallel between the installation area E for the container and the
same common sensor 18, in the sense that the two optical systems
24, 24' form an image of the same object in the installation area
on the same sensor 18, i.e. each between the installation area E
for the container and an associated sensor 18, 18', in which case,
the two optical systems 24, 24' each form an image of the same
object in the installation area on the associated sensor 18, 18'.
It is considered that there is for each image point, an upstream
path downstream of the light rays starting from a source,
reflecting on the object, then entering the optical observation
system to be deflected therein by dioptric and/or catoptric optical
elements, filtered (modification of their spectral composition or
their polarization), intersected by a diaphragm, etc. in order to
form an image of the object on the sensitive surface of the sensor.
An element "optically interposed" between a first and a second
other element therefore means that by following the path of the
light rays contributing to the image, said element is located on
said path downstream of the first element and upstream of the
second element.
[0097] In the embodiments of FIGS. 1A, 4, 5, 7A or 7B, the two
optical systems are associated with the same common sensor 18. In
this case, it is possible, notionally, to dissociate this single
common sensor into two sensors, namely a first sensor associated
with a first optical system 24 and a second sensor associated with
a second optical system 24'. In reality, in this case, it will be
possible to have a common sensor whose first part of the image
capture surface, or first image formation area, is dedicated to the
first optical system 24 and whose second part of the image capture
surface, or second image formation area, is dedicated to the second
optical system 24'. In this case, the first part of the common
sensor forms a first sensor 18 and the second part of the common
sensor forms the second sensor 18'.
[0098] In the embodiment of FIG. 3, the two optical systems 24, 24'
are each associated with its own associated sensor, with a first
optical system 24 associated with a first sensor 18, and a second
optical system 24' associated with a second sensor 18'.
[0099] Each optical system 24, 24' defines, for the associated
sensor, an upstream field-of-view in the installation area, defined
as all the points of the installation area which are likely to be
imaged by the optical system considered on the considered sensor.
In this upstream field-of-view, the first and second optical
systems 24, 24' define respectively, for the associated sensor, a
first and a second peripheral observation field. It is arbitrarily
considered here that the upstream and the downstream correspond to
the upstream path downstream of a light ray coming from the
installation area and moving in the direction of the associated
sensor.
[0100] Each optical system 24, 24' can thus form on the associated
sensor an image of the same ring surface 16 of a container 14
placed in the installation area E, each image being formed by the
rays propagating from the ring surface according to the
corresponding peripheral observation field.
[0101] In the exemplary embodiments, at least the first optical
system 24 comprises, in addition to the optical lens system 20, at
least one optical element 122, 261, which is here arranged between
the lens system 20 and the installation area E. The entire first
optical system 24 between the first sensor 18 and the installation
area thus comprises the lens system 20 and the optical element(s)
122.
[0102] In the embodiments of FIGS. 1A, 5, 7A and 7B, the second
optical system 24' comprises, in addition to an optical lens system
20', in this common case for the two optical systems 24, 24', at
least one optical element 122, 262, which is here arranged between
the lens system 20' and the installation area.
[0103] In the embodiments of FIGS. 3, 4, 7A and 7B, the second
optical system 24' only comprises an optical lens system 20', with
no reflection surface of revolution between the lens system 20' and
the installation area, In the embodiment of FIG. 4, the second
optical system 24' comprises an optical lens system 20 entirely
common with that of the first optical system 24, 24'. In the
embodiment of FIG. 3, the second optical system 24' comprises a
second optical lens system 20' which is only partially common with
the first optical lens system 20' of the first optical system 24.
Thus, the example of FIG. 3 includes a first optical lens system 20
and a second optical lens system 20' which incorporate a common
separation blade 21, which can be dichroic, arranged at 45 angle
degrees on the installation axis A'1, to separate optical rays
coming from the installation area into two parts. A first part of
these optical rays is sent towards a first sensor 18, belonging in
this example to a first camera 19, and another part is sent towards
a second sensor 18', belonging in this example to a second camera
19'. In the example, the first and second lens systems 20, 20' have
common elements, including for example a telecentricity lens and
the separation blade 21, and elements specific to each of them,
namely optical elements which are interposed between the separation
blade 21 and the respective sensors 18, 18'. The focal distances of
the lens systems 20 and 20' can be different.
[0104] In some of the illustrated examples, the optical lens system
20, 20' associated with either of the sensors 18, 18' is a
telecentric lens system. A telecentric lens system is well known to
those skilled in the art of the machine vision devices because it
is used to form on the sensor an image which includes no or almost
no parallax effect. In optical theory, a telecentric lens system is
a lens system whose entrance pupil is positioned infinitely. It
follows that such a lens observes in its field-of-view according to
main observation rays which, through the associated optical system
24, 24', pass through the center of the entrance pupil CO of the
lens system 20, 20', and which are parallel or almost parallel to
the optical axis, hence the absence of parallax effect. However,
the optical lens system 20, 20' is not necessarily telecentric, as
illustrated by the embodiment of FIG. 4.
[0105] A sensor 18, 18' generally has a rectangular or square,
therefore two-dimensional, shape so that it delivers a
two-dimensional digital image representative of the two-dimensional
optical image formed on the sensor by the optical lens system 20,
20'. The entire digital image delivered by such a sensor 18, 18'
will be called overall image IG, IG'. It will be seen later that,
in this overall digital image, only one or more image area(s) will
be useful. Preferably, the overall image IG, IG' is acquired during
a single integration time (also called exposure time) of the
sensor. Alternatively, two acquisitions very close in time are made
such that the article moves only insignificantly between the two
acquisitions.
[0106] The optical axis of the lens system 20, 20' is preferably
coincident with the installation axis A'1. In some cases, this
optical axis is not straight, but segmented, for example by
integration of a send-back mirror into the lens system or upon use
of a separation blade 21. It is thus possible to provide a
send-back mirror at 45 angle degrees with respect to the
installation axis, thus with a first segment of the optical axis,
on the sensor side, which would be arranged at 90 angle degrees
with respect to the installation axis, and a second segment, on the
other side of the send-back mirror, which would be arranged in line
with the installation axis A1. Thus, in the example of FIG. 3
including a first and a second physically distinct sensors 18, 18',
associated respectively with a first and a second optical system
20, 20', the second lens system 20' presents, due to the presence
of a separation blade 21 which returns some of the light rays at 90
angle degrees in the direction of the second sensor 18', a
downstream segment of optical axis, on the side of the second
sensor 18', which is arranged at 90 angle degrees with respect to
the installation axis A'1, and an upstream segment, on the other
side of the separation blade 21, which is arranged in line with the
installation axis A1. For the record, it is here considered
arbitrarily that the upstream and downstream correspond to the
upstream path downstream of a light ray coming from the
installation area and moving in the direction of the associated
sensor.
[0107] In the examples illustrated, the first optical system 20 is
arranged vertically along the axis A'1, and it is turned downwards
to observe the installation area E below the device, so to observe
from above, i.e. from the top, a possible container 14 arranged in
the installation area. The first photoelectric sensor 18, which in
the embodiments of FIGS. 1A, 4, 5, 7A and 7B, is a common sensor
associated with the two optical systems 24, 24', is therefore at
the apex of the device 10 and it is turned downwards in the
direction of the installation area E. With this disposition, it is
understood that the theoretical ring surface of a container 14
placed in the installation area is therefore contained in a plane
parallel to the plane of the sensor. This remains true for the
example in FIG. 3 if the tilting of the optical axis which is
induced by the presence of the separation blade 21 is considered.
Thus, with a simple telecentric lens, without any other optical
system, the image of the ring surface which would be formed on a
single sensor would not allow to "see" unevenness. On the contrary,
no height variation in this ring surface would be visible. This
will however be implemented for the second optical system of FIG.
3.
[0108] In practice, the installation axis A'1 will be defined as
being the extension in the installation area E of the optical axis
of the first optical system 24.
[0109] According to another aspect of the invention, it is provided
that the actual ring surface 16 of the container is lighted by
means of at least a first peripheral incident light beam, that is
to say extending to 360 angle degrees about the installation axis
A'1. The ring surface is lighted from above, in the sense that
first incident light rays arrive on the ring surface 16 coming from
points located above the plane PRef perpendicular to the
theoretical central axis A1 and tangent to a point of the ring
surface, preferably the highest point along the direction of the
theoretical central axis A1. The first light beam comprises, for a
whole series of radial planes distributed at 360 angle degrees
about the installation axis A.sup.11, first incident radial light
rays contained in these radial planes containing the installation
axis. The radial rays are, at least for some of them, directed
towards the installation axis A'1, as illustrated in FIG. 2. These
first incident radial light rays are, at least for most of them,
not perpendicular to this axis. The incident radial light rays are
preferably non-parallel to each other and, in the method
illustrated in FIG. 1A, the peripheral incident light beam
comprises, in a given radial half-plane Pri (illustrated in FIG.
1B), containing the installation axis and delimited by the
installation axis, non-parallel incident radial light rays. Thus,
FIG. 1A illustrates that the first peripheral incident light beam
may contain incident radial light rays which form an elevation
angle, with a plane perpendicular to the installation axis,
preferably comprised between 0 and 45 degrees. Preferably, the
first light beam contains incident radial light rays in a
continuous or substantially continuous angular range. This range
can have an angular extent of at least 30 degrees or more. The rays
contained in this range can form an elevation angle, with a plane
perpendicular to the theoretical central axis, comprised between 5
and 40 degrees.
[0110] In addition to the first radial rays, the first peripheral
incident light beam may also contain non-radial incident light
rays.
[0111] In the illustrated embodiments, the device 10 includes at
least a first lighting system intended to ensure the lighting of
the ring surface according to the first peripheral incident light
beam. It is thus the rays derived from this first lighting system
that are reflected by the ring surface and collected at least by
the first optical system according to at least the first
observation field to be directed towards the first sensor 18. In
the illustrated embodiments, this first lighting system includes a
first light source 28 which is annular and the axis of which is the
installation axis, and which is arranged above the installation
area. The first light source 28 has a diameter greater than the
diameter of the ring surface 16.
[0112] In the example illustrated, the diameter of the first
annular light source 28 is greater than the diameter of the annular
crown 122 which carries at least the primary reflection surface
261. In this embodiment, the light source 28 is arranged
substantially at the same height along the direction of the
installation axis A'1. as the lower primary reflection surface 261.
However, this position is purely illustrative and could be adapted
as a function of the diameter and of the axial position of the ring
surface of the container to be inspected.
[0113] Note that FIG. 2 illustrates a variant of the embodiment of
FIG. 1A which differs only in that the lighting system includes, in
addition to the annular light source 28, a reflector 140 arranged
just below the annular light source 28. This reflector 140 here
includes a frustoconical surface, turned in the direction of the
installation axis. The surface of the reflector 140 is flared
upwards and therefore has a diameter substantially identical to
that of the light source 28. It reflects substantially vertical
rays, emitted by the light source 28, in the direction of the
installation area, according to a grazing incidence, in the
direction of the ring surface. Such a reflector makes it possible
to concentrate the light emitted by the light source 28 in the
direction of the ring surface, under a grazing incidence favorable
for the embodiments which have a first grazing observation
elevation angle, that is to say less than 25 angle degrees.
[0114] In the embodiment of FIG. 1A, and also for that of FIG. 7B,
for which the first and second observation elevation angles differ
by less than 20 angle degrees, the first light source 28 is the one
that also provides the light intended to form the second image of
the ring surface 16 through the second optical system 24'. However,
in either case, it is possible to provide for the presence of a
second light source dedicated to the formation of the second image
of the ring surface 16 through the second optical system 24'.
[0115] Indeed, for the embodiments of FIGS. 3, 4, 5, and 7A, it is
planned to provide a second lighting system, separate from the
first one, and intended to ensure the lighting for the ring
surface. It is thus at least mainly the rays derived from this
second lighting system that are reflected by the ring surface 1.6
and that are collected according to the second observation field in
the direction of the second sensor 18' or of the common sensor.
This second lighting system includes a second light source 28' and
is able to provide a second peripheral incident light beam, here
distinct from the first one, comprising second incident radial
light rays contained in radial planes containing the installation
axis A'1 and distributed to 360 angle degrees about the
installation axis A'1. They light the installation area, and
therefore a ring surface 16 caused to be there, from the top.
[0116] In the examples of FIGS. 3 and 5, said second incident
radial light rays are directed so as to move away from the
installation axis A'1 when followed from the second light source
28', which second light source 28' is, as in the other embodiments,
arranged above the reference plane Pref of the ring surface 16.
[0117] In the embodiment of FIG. 3, the second light source 28' is
annular and has the installation axis as its axis and it has a
diameter which is slightly smaller than the diameter of the ring
surface 16. Preferably, these two diameters will be very close, in
order to have a direction of incidence of light rays derived from
the second light source 28' close to 90.degree. with respect to a
reference plane perpendicular to the installation axis. In the
embodiment of FIG. 5, the second light source 28' is a central
source, which can be considered as a point source and placed on the
installation axis A'1. It therefore also has a diameter which is
smaller than the diameter of the ring surface 16. In this way, the
ring surface 16 is lighted from the installation axis A'1, in other
words, from inside.
[0118] FIG. 4 illustrates a possible variant for the second light
source 28'. In such a variant, the light source 28' can be annular,
can have the installation axis as its axis, and have a diameter
which is greater than the diameter of the ring surface 16. It is
also placed above the optical elements 122 and 132. In this case,
it is noted that the second radial rays are directed towards the
installation axis A'1 when followed from the second light source
28', which is arranged above the reference plane Pref of the ring
surface 16. This variant is also implemented in the embodiment of
FIG. 7A, and it can also be implemented as part of the embodiment
of FIG. 3.
[0119] Preferably, for each observation field, it is provided that
the incident beam lights the ring surface 16, from the top, at an
incidence such that, at the point of reflection T' of an incident
ray, whose ray reflected by the actual ring surface is seen by the
associated sensor through the associated optical system, the normal
"n" to the ring surface forms with respect to the axis A'1 an angle
less than 30 angle degrees, preferably less than 10 angle degrees.
Within the context of a perfect geometry, with an actual ring
surface corresponding to the theoretical ring surface, it is thus
ensured that the light reflected by the ring surface which is seen
by the sensor 18 is the light which is reflected by the locally
highest point, or close the highest local point of the ring
surface. Only what is happening in a radial half-plane Pri of the
device and of the ring surface to be controlled is considered here.
Thus, the locally highest point of the ring surface is the point
which, in the profile of the ring surface in this radial half-plane
Pri, is the highest point along the direction of the installation
axis. Furthermore, the locally highest point can be generally
defined as being the one for which the normal to the ring surface
is parallel to the installation axis. FIG. 2 illustrates an
incident ray RI1 emitted by the light source, which is reflected by
a point Ti of the ring surface at a first reflected ray RR1 which
is intercepted by the first primary reflection surface 261 and thus
sent towards the associated sensor. Another incident ray RI2 is
reflected along a second ray RR2 reflected by the same point Ti of
the ring surface at a second reflected ray which is intercepted by
the second primary reflection surface 262 and thus sent towards the
associated sensor. For the illustration, the normal "n" to the ring
surface 16, at the point Ti, is substantially parallel to the
direction of the installation axis, and the point Ti is the locally
highest point of the ring surface profile in the corresponding
radial half-plane. Within the context of the device, this condition
will be fulfilled by selecting the appropriate position of the
light source(s) 28, 28'. This position, which can be for example
defined by the diameter of the annular source 28, 28', and by its
height position along the direction of the installation axis A'1,
indeed defines the angle of incidence of the rays which are likely
to light the ring surface. Of course, the diameter and the height
position of the actual ring surface 16 determine, in combination
with the orientation of the normal to the point of reflection on
the ring surface, which rays emitted by the source 28 are likely to
be reflected in the direction of the sensor. It is therefore
understood that for each ring surface diameter, it could be useful
to adapt either the diameter of the annular source, or its height
position relative to the ring surface 16. However, it is not
necessarily critical to detect the locally highest point of the
ring surface. Indeed, within the context of a planar and annular
ring surface, the inner and outer radial edges of the ring surface
have a ridge wherein, if the point of reflection of the incident
light is located on this ridge, the height difference between the
reflection point and the locally highest point will be in this case
considered as insignificant. Within the context of a ring surface
whose profile in the radial half-plane is rounded, it will also be
considered that the fact that the reflection can be done on a point
which is not the locally highest point, is largely compensated by
the fact that this situation is repeated over the entire periphery
at 360 angle degrees so that, from a point of view of the analysis
of the evenness for example, the error thus made is generally
considered as insignificant. Thus, it is certainly possible to
provide a device in which the light source(s) would be adjustable,
by adjustment of the radial position or of the position along the
direction of the installation axis, to adjust the angle of
incidence of the light beam on the ring surface. However, such a
disposition is not mandatory. In order to best cover a wide range
of ring surface diameter, it can be planned that the device is
provided with several annular light sources, for example offset
along the direction of the installation axis and/or of different
diameter, these different light sources can be used simultaneously
or alternatively depending on the diameter and shape of the ring
surface of a container to be inspected. In practice, light sources
are generally used which have, in a radial plane, an extent
according to the radial direction and which emit a light beam
containing radial rays at a continuous or substantially continuous
angular range which can have an angular extent of at least 30
degrees or more. Such light sources, which have a radial extent and
which are diffuse, make it possible to adequately light a whole
series of containers having ring surfaces having a diameter, a
profile and a height position which may differ in some ranges,
without requiring position adaptation.
[0120] Note that, in particular in the embodiment of FIG. 1A, or in
that of FIG. 7B, it will be advantageous to provide that the
difference between the two observation elevation angles .gamma.1,
.gamma.2 is less than or equal to 20 angle degrees, which will
limit the errors that could be induced by reflections which, for
the two images of the ring surface, would be made at different
points of the ring surface which, while being in the same radial
plane could be offset radially and axially from each other. This
will be in particular advantageous insofar as it will promote the
possibility of using a common light source for the observation
according to the two observation elevation angles.
[0121] In the embodiments having a large difference between the
observation elevation angles .gamma.1, .gamma.2, it will be
preferably provided two distinct light sources 28, 28' arranged so
that, in a given radial plane Pri, the first and second incident
beams light the ring surface at an incidence such that the rays
reflected by the actual ring surface 16 are seen through the two
optical systems after reflection at the same point of the ring
surface. But it can be accepted that the reflection points are
different, because this can be taken into account in the processing
of the images.
[0122] In the illustrated examples, for an optical system 24, 24',
the sensor 18, 18', its lens system 20, 20', the optional optical
element 122 and the installation area are aligned in this order
along the same optical axis corresponding to the installation axis
A'1.
[0123] In the illustrated examples, the optical peripheral vision
element 122 includes at least a first primary reflection surface
261 belonging to the first optical system 24. In the example of
FIG. 1A, the same optical element 122 includes a second primary
reflection surface 262 belonging to the second optical system 24',
so that the optical element 122 is common to the two optical
systems, but by means of two different primary reflection surfaces.
In the example of FIG. 5, a second distinct optical element 122'
includes the second primary reflection surface 262 belonging to the
second optical system 24'.
[0124] The first primary reflection surface 261 and, for the
embodiments which provided with it, the second primary reflection
surface 262, are arranged in a downstream field-of-view of the
associated sensor 18, 18', that is to say in the portion of the
field-of-view of the sensor which, in the examples illustrated, is
defined by the associated lens system 20, 20'. The upstream
field-of-view is therefore the one that is outside the associated
optical system 24, 24', upstream thereof in the direction of
circulation of the light from the installation area towards the
associated sensor.
[0125] In the examples illustrated, the first primary reflection
surface 261 and the possible second primary reflection surface 262
are frustoconical surfaces of revolution generated by rotation,
each of its own generating line segment, about the same axis, here
the installation axis A'1, and they are arranged to reflect light
rays, coming from the ring surface, in the direction of the
associated sensor, through the associated lens system 20, 20'. They
have therefore specular reflection properties. They can be
advantageously formed by a mirror, but they can also be made in the
form of a prism, i.e. an optical diopter.
[0126] In the illustrated embodiments, the first primary reflection
surface 261, and the possible second primary reflection surface
262, is a frustoconical surface of revolution, concave in a plane
perpendicular to the installation axis A'1, which is turned towards
the installation axis A'1, and which can for example be formed on
an inner face of an annular crown, for example of the optical
element 122, 122'. In this way, each primary reflection surface
261, 262 can return, directly or indirectly, in the direction of
the installation axis A'1, light rays coming from the actual ring
surface at a corresponding observation elevation angle .gamma.1,
.gamma.2.
[0127] For a given peripheral observation field, the observation
rays are the rays derived from the installation area E and likely
to be received by the associated sensor 18, 18' through the
associated optical system 24, 24'. Among these rays, the main
observation rays are those which, through the associated optical
system 24, 24', pass through the center of the entrance pupil CO of
the lens system 20, 20'. The observation elevation angle of a main
observation ray corresponds to the angle, with respect to a
reference plane of the installation Pref' perpendicular to the
installation axis A'1, of a main observation ray in the
installation area where it is likely to affect the ring surface of
a container to be inspected. It can be arbitrarily considered that
the observation rays propagate from upstream to downstream starting
from the observation area in the direction of the associated sensor
18, 18'.
[0128] Within the context of a device provided with a telecentric
optical system, the main observation rays received by the sensor
all enter the lens system 20, 20' in parallel. If in addition, as
in some of the illustrated systems, the optical system includes as
first optical element according to the upstream-downstream
propagation of light from the installation area towards the
associated sensor, a primary frustoconical reflection surface 261,
262 generated by a line segment, the observation elevation angle
.gamma.1, .gamma.2 of the corresponding peripheral observation
field is then a single angle for any main observation ray belonging
to this given peripheral observation field, and it can be directly
deduced from the inclination of the corresponding primary
reflection surface 261, 262 with respect to the installation axis
A'1. This angle is then considered as being the observation
elevation angle .gamma.1, .gamma.2 of the peripheral observation
field.
[0129] However, in some cases, in particular the case of a device
having no telecentric lens system, the observation rays received by
the sensor, including the main rays, may have observation elevation
angles different relative to each other within a peripheral
observation field determined by a given optical system 24, 24'. In
this case, it can be assumed that the observation elevation angle
of a peripheral observation field is the angle, measured in the
installation area where it is likely to affect the ring surface of
a container to be inspected, with respect to a plane perpendicular
to the installation axis A'1, of a main average observation ray.
The main average ray of a peripheral observation field is the one
that presents an observation elevation angle which is the
arithmetic mean of the minimum and maximum values of the
observation elevation angles for the main rays of the considered
field.
[0130] Preferably, in all the embodiments, the first and/or the
second peripheral observation field is without azimuthal breakage
about the installation axis A'1. In particular, there is no
azimuthal angular discontinuity between two infinitely close
observation radial rays angularly about the installation axis. In
this way, there is no point breakage seen in the image generated by
the considered field, which could make the image more difficult to
interpret. For this, the first and/or the second primary reflection
surface 261, 262 is preferably without discontinuity of curvature
about the installation axis A'1, the curvature being analyzed in a
plane perpendicular to the installation axis A'1, to ensure a field
of observation without azimuthal breakage. The primary reflection
surfaces 261, 262 are also preferably azimuthally continuous in the
sense that they are continuously reflecting about the installation
axis A'1, without masked angular sector, to ensure the azimuthal
continuity of the observation field. However, in some cases, in
particular due to hardware installation constraints, by the
presence of a power cable, one or more angular sector(s), about the
installation axis, may be masked. Preferably, such a masked
azimuthal angular sector will be of small or very small extent,
preferably less than 5 degrees about the installation axis.
[0131] The first and/or the second observation field(s) is/are
peripheral in the sense that the corresponding observation radial
rays are distributed in radial planes at 360 angle degrees about
the installation axis A'1. In the examples, the first peripheral
observation field is symmetrical in rotation about the installation
axis A'1. Likewise, the second peripheral observation field is
symmetrical in rotation about the installation axis A'1.
[0132] The first and/or the second peripheral observation field(s)
observe(s) "from above" in the sense that the ring surface is
observed from above a plane Pref perpendicular to the theoretical
central axis A1 of the ring surface, and containing at least one
point of the ring surface, for example the highest point along the
direction of the theoretical central axis A1.
[0133] In the embodiments illustrated in FIGS. 1A to 5, the first
optical system 24, possibly the second optical system 24', further
includes, optically interposed between the optical element 122 and
the lens system 20, a send-back reflection surface 132. Thus, as
can be seen in FIG. 1A, the rays reflected by the two primary
reflection surfaces 261, 262 are intercepted by the send-back
reflection surface 132. The send-back reflection surface 132 is
arranged in the downstream field-of-view of the sensor 18, this
downstream field-of-view being defined by the optical lens system
20, 20'. In the example, this send-back reflection surface 132
includes a convex surface of revolution turned away from the
installation axis A'1, so as to return the rays in the direction of
the sensor. Preferably, the send-back reflection surface 132 is a
convex frustoconical surface the axis of which is the installation
axis A'1. The send-back reflection surface 132 is therefore formed
on the outer surface of a truncated cone. In some embodiments, it
has a small diameter and a large diameter which are both smaller
than the diameter of the ring surface of a container to be
controlled, but this characteristic is only compulsory for the
embodiments for which the second optical system 24' to provide the
second associated sensor 18' with a direct vision of the ring
surface 16, as in the embodiments of FIGS. 3 and 4. The large
diameter is arranged below the small diameter.
[0134] The send-back reflection surface 132 is part of the
downstream field-of-view defined by the lens system 20 for the
first sensor 18. In the embodiment of FIG. 1A, the send-back
reflection surface 132 is also part of the downstream field-of-view
defined by the lens system 20' for the second sensor 18', here the
common sensor.
[0135] In the embodiments of FIGS. 1A to 5, the first primary
reflection surface 261 and, for the embodiment of FIG. 1A, also the
second primary reflection surface 262, while being a surface of
revolution the axis of which is the installation axis A'1, is
therefore arranged to indirectly reflect light rays, coming from
the actual ring surface at respective observation elevation angles
.gamma.1, .gamma.2, in the direction of the associated sensor 18,
18'. Indeed, the reflection on each of the primary reflection
surfaces 261, 262 is indirect because followed by at least one
reflection, here on the send-back reflection surface 132, before
reaching the associated sensor 18, 18'.
[0136] In the exemplary embodiments of FIGS. 7A and 7B, the
reflection, on the first primary reflection surface 261, of the
light rays coming from the ring surface towards the associated
sensor, is a direct reflection, with no other reflection surface
between the ring surface 16 and the sensor 18 for a given light ray
derived from the ring surface.
[0137] In the exemplary embodiment illustrated in FIG. 5, the
reflection, on the second primary reflection surface 262, of the
light rays coming from the ring surface towards the associated
sensor, is a direct reflection, with no other reflection surface
between the ring surface 16 and the sensor 18 for a given light ray
derived from the ring surface.
[0138] In the case of an indirect reflection, it is advantageously
provided that the trajectory of the main rays between each of the
primary reflection surfaces 261, 262 and the send-back reflection
surface 132 is perpendicular or substantially perpendicular to the
installation axis. Such a disposition makes it possible to
considerably reduce the sensitivity of the device to a possible
defect in centering of the primary reflection surfaces 261, 262 or
of the send-back reflection surface 132. For this, the
frustoconical send-back reflection surface 132 has an apex
half-angle of 45 angle degrees and it is arranged at the same
height along the direction of the installation axis A'1 as the
primary reflection surfaces 261, 262. Each primary reflection
surface 261, 262 presents in this case an apex half-angle a1, a2
which is equal to half of the corresponding observation elevation
angle .gamma.1, .gamma.2 desired for the considered primary
reflection surface 261, 262. Thus, for a desired observation
elevation angle .gamma.1 of 15 angle degrees, the first primary
reflection surface 261 has a conicity whose apex half-angle a2 is
equal to 7.5 angle degrees, the first primary frustoconical
reflection surface 261 being flared downwards, with its large
diameter arranged below its small diameter along the direction of
the installation axis. In this configuration, it is particularly
advantageous that, in addition, the lens system 20, 20' is
telecentric, so that the trajectory of all the main rays between
each of the primary reflection surfaces 261, 262 and the send-back
reflection surface 132 is perpendicular or substantially
perpendicular to the installation axis A'1.
[0139] However, as a variant, still in the case of an indirect
reflection, the send-back reflection surface 132 could be a
frustoconical surface having an apex half-angle smaller than 45
angle degrees, for example equal to 45 angle degrees, minus an
angle .delta. (delta). In this case, the send-back reflection
surface 132 may be disposed above the level of the primary
reflection surface(s) 261, 262, and the primary reflection
surface(s) 261, 262 would then have an apex half-angle a1, a2 equal
to half of the desired observation elevation angle .gamma.1,
.gamma.2, minus the value of the angle .delta. (delta).
[0140] In the example of FIG. 1A, the first primary reflection
surface 261. and the second primary reflection surface 262 are
arranged to work both in indirect reflection jointly with a
send-back reflection surface 132, and they are advantageously
offset axially while being directly attached to each other along
the direction of the installation axis, that is to say they are not
arranged axially at the same level. Arbitrarily, it is considered
that the primary reflection surface which is located below the
other one along the direction of the installation axis A'1 is the
first primary reflection surface 261, the second primary reflection
surface 262 being then arranged above the first one. The two
primary reflection surfaces can then have a common circular ridge
corresponding to the lower edge of the upper surface, here the
second primary reflection surface 262, and to the upper edge of the
lower surface, here the first primary reflection surface 261.
[0141] However, the first primary reflection surface 261 and the
second primary reflection surface 262 could be offset axially by
being axially separated by a non-zero axial deviation between the
lower edge of the upper surface and the upper edge of the lower
surface, as in the example of FIG. 5.
[0142] In the illustrated embodiments, it can be seen that, with
respect to the axis A1 of the ring surface, the observation made
via a primary reflection surface is made peripherally radially from
outside relative to the ring surface, in the sense that the first
primary reflection surface 261, and moreover also the second
primary reflection surface 262 for the embodiments of FIGS. 1A and
5, is arranged radially outside relative to the diameter of the
ring surface 16.
[0143] It is noted however that for the embodiments of FIGS. 1A to
7A, an observation ray of the first observation field, coming from
the ring surface 16, is intercepted by the first primary reflection
surface 261 at a point diametrically opposite the point of origin
on the ring surface, along a long path which intersects the
installation axis A'1. Thus, it can be seen that the ring surface
16 is observed, according to at least the first observation field,
through the side of its internal edge, that is to say the
observation rays, in their trajectory from the ring surface towards
the sensor, are directed towards the installation axis when they
leave the ring surface 16 in the direction of the first primary
reflection surface 261, and they intersect this installation axis
A'1 before reaching the first primary reflection surface 261.
[0144] In the embodiment of FIG. 7B, the first optical system 24
defines an observation peripheral field radially from outside and
observing the ring surface from the side of its external edge.
Thus, a first observation ray coming from the ring surface 16 does
not intersect the installation axis A'1 between the ring surface
and the first optical system 24.
[0145] In the embodiment of FIG. 1A, the second optical system 24'
defines, like the first one, a peripheral observation field
radially from outside and observing the ring surface through the
side of its internal edge, therefore according to observation rays
which intersect the installation axis A'1 when the installation
axis and the theoretical central axis A1 are coincident.
[0146] In the embodiment of FIG. 3, the second optical system 24',
without reflection surface of revolution, therefore in telecentric
direct vision defines, with respect to the theoretical central axis
A1 of the ring surface, an observation perpendicular to the
reference planes of the installation and of the ring surface.
[0147] In the embodiments of FIGS. 4, 7A and 7B, the second optical
system 24', without a reflection surface of revolution, therefore
in a non-telecentric direct vision, defines, with respect to the
axis A1 of the ring surface, an observation radially from inside
relative to the ring surface. However, in this embodiment of FIG.
4, the ring surface 16 is observed, according to the second
observation field, through the side of its internal edge, as for
the first embodiment.
[0148] In the embodiment of FIG. 5, the second optical system 24',
defines a peripheral observation field radially from outside and
observing the ring surface through the side of its external
edge.
[0149] In the embodiments of FIGS. 3, 4, and 5, a second
observation ray coming from the ring surface 16 does not intersect
the installation axis A'1 between the ring surface and the second
optical system 24'.
[0150] In all of the illustrated embodiments for which the optical
system includes a primary reflection surface arranged for a direct
or indirect reflection, the primary reflection surface has a small
diameter and a large diameter both greater than the diameter of the
theoretical ring surface, so that it defines a peripheral
observation field radially from outside. In cases where the primary
reflection surface is arranged for an indirect reflection, it is
preferably flared in the direction of the installation axis towards
the installation area. On the contrary, in the configurations of
the embodiments of FIGS. 5, 7A and 7B, with an optical system 24,
24' including a primary reflection surface 261 and/or 262 which is
arranged for a direct reflection towards the sensor, said primary
reflection surface 261. and/or 262 can be flared in the direction
of the installation axis towards the associated sensor, or be
cylindrical of revolution about the installation axis A'1.
[0151] In the embodiments of FIGS. 1A to 5, the first peripheral
observation field, defined for the first sensor or for the common
sensor by the first optical system 24 including the first primary
reflection surface, has, with respect to a plane PRef perpendicular
to the installation axis A'1, a first observation elevation angle
.gamma.1, which is for example comprised between 5 and 25 angle
degrees, for example 15 angle degrees. In the illustrated examples,
the first peripheral observation field comprises the observation
rays according to which incident light rays are reflected by the
first primary reflection surface 261 towards the sensor 18. In
other words, this first peripheral observation field constitutes a
first upstream portion CAM1 of the field-of-view of the first
sensor 18 through the first optical system 24, as determined by the
first primary reflection surface 261, in the installation area E up
to this first primary surface 261.
[0152] For the embodiments of FIGS. 7A and 7B, the first peripheral
observation field, defined for the first sensor or for the common
sensor by the first optical system 24 including the first primary
reflection surface, has, with respect to a plane PRef perpendicular
to the installation axis A'1, a first observation elevation angle
.gamma.1, which, for FIG. 7A, is comprised in the range from 25 to
45 angle degrees, and which, for FIG. 7B, is greater than 45 angle
degrees.
[0153] For the embodiments of FIGS. 1A to 5, as well as that of
FIG. 7A, in the upstream portion of the observation rays which is
in the installation area E up to this first primary reflection
surface 261, the first radial observation rays determined by the
first optical system are first centripetal when followed from the
ring surface, therefore oriented in the direction of the
installation axis A'1, then intersect the installation axis A'1 to
become, beyond the installation axis, centrifugal in the direction
of the first primary reflection surface 261 of the first optical
system, until affecting this first primary reflection surface
261.
[0154] For the embodiment of FIG. 7B, in direct reflection by the
first primary reflection surface 261 without other reflection on a
reflection surface of revolution, the first radial observation rays
determined by the first optical system are, when followed from
upstream to downstream from the ring surface in the direction of
the sensor, centrifugal relative to the installation axis A'1,
until affecting the first primary reflection surface 261 of the
first optical system 24.
[0155] The second peripheral observation field has, with respect to
a plane PRef perpendicular to the installation axis A'1, a second
observation elevation angle .gamma.2, which is for example
comprised between 20 angle degrees and 90 angle degrees, this
second angle being different from the first observation elevation
angle .gamma.1.
[0156] Preferably, the first and second observation elevation
angles differ by at least 5 angle degrees. Indeed, such an angular
difference appears necessary for good accuracy of the triangulation
operations which will be described later. In the illustrated
examples, but arbitrarily, the second observation elevation angle
.gamma.2 is strictly greater than the first observation elevation
angle .gamma.1.
[0157] In the examples illustrated in FIGS. 1A and 5, the second
peripheral observation field comprises the observation rays
according to which incident light rays are reflected on the second
primary reflection surface 262, therefore through the second
optical system 24', in the direction of the second sensor 18', in
this case formed by the common sensor. This second peripheral
observation field constitutes a second upstream portion CAM2 of the
field-of-view of the common sensor 18, 18' through the second
optical system 24', as determined by the second primary reflection
surface 262, in the installation area E up to the second primary
reflection surface 262.
[0158] For the embodiment of FIG. 1A, in the upstream portion of
the second observation rays which is in the installation area E, up
to this second surface 261, 262, the second radial observation rays
determined by the second optical system are first centripetal when
followed from upstream to downstream from the ring surface in the
direction of the sensor, therefore first oriented in the direction
of the installation axis A'1, then intersect the installation axis
A'1 to become centrifugal beyond the installation axis A'1 in the
direction of the second primary reflection surface 262 of the
second optical system 24', until affecting the second primary
reflection surface 262.
[0159] In the embodiment of FIG. 1A, the second observation
elevation angle .gamma.2 is, like the first observation elevation
angle .gamma.1, a grazing angle, less than 25 angle degrees.
[0160] In the embodiment of FIG. 5, in direct reflection by the
second primary reflection surface 262 without any other reflection
on a reflection surface of revolution, the second observation
elevation angle .gamma.2 is a downward angle, greater than 65 angle
degrees, preferably greater than 75 angle degrees. For this
embodiment of FIG. 5, the second radial observation rays determined
by the second optical system are, when followed from upstream to
downstream from the ring surface in the direction of the sensor,
centrifugal with respect to the installation axis A'1, until
affecting the second primary reflection surface 262 of the second
optical system 24'.
[0161] It is noted that, in the embodiments of FIGS. 1A and 5 which
have in common the presence of the second reflection surface 262
and the presence of a common sensor 18, the first primary
reflection surface 261 and the second primary reflection surface
262 are each in disjoint portions of the downstream field-of-view
of the common sensor 18, in the sense that they can be seen
simultaneously by the sensor through the lens system 20, without
masking each other. Insofar as the one would partially mask the
other, for the one which is partially masked only the useful
unmasked part will be considered.
[0162] In the embodiments of FIGS. 3 and 4, in direct vision
without reflection on a reflection surface of revolution, the
second observation elevation angle .gamma.2 is also a downward
angle, greater than 65 angle degrees, preferably greater than 75
angle degrees. In the embodiment of FIG. 3, the presence of a
telecentric lens system means that the second observation elevation
angle .gamma.2 is equal to 90 angle degrees. Also in these two
embodiments, this second peripheral observation field constitutes a
second upstream portion CAM2 of the field-of-view, of the common
sensor 18 for the embodiment of FIG. 4, or of the second sensor 18'
for the embodiment of FIG. 3, through the second optical system as
determined by the lens system 20'. In the portion of the
observation rays which is in the installation area E up to the lens
system 20', the observation rays of this second observation field
are, for the embodiment of FIG. 4, centripetal towards the axis A'1
or, for the embodiment of FIG. 3, parallel to this axis, when they
are followed from the installation area E towards the lens system
20'. It is noted that, in these embodiments not including a
reflection surface of revolution for the second optical system 24',
which is then reduced to the lens system 20', it can be considered
that the upstream portion and the downstream portion of the
field-of-view for the second sensor, distinct or common, are
coincident.
[0163] It is therefore noted that the upstream portion of the
second field-of-view is of annular section through a plane
perpendicular to the installation axis A'1. In the two embodiments
of FIGS. 3 and 4, the inner limit of this annular area is
determined by the outer contour of the send-back surface 132, or
even by the outer contour of the second annular light source 28'
for the example of FIG. 3. Its outer limit is determined by the
inner contour of the optical element 122, or by a possible second
annular light source 28' in the embodiment of FIG. 4, or by the
field limit of the associated sensor 18, 18'.
[0164] In the embodiment of FIG. 3, the second sensor 18' being a
dedicated sensor, it is possible to provide for a specific
positioning of the second sensor or a specific focusing of the
second lens system 20', which allows taking into account the
relatively significant path length difference for, on the one hand,
the rays through the first optical system 24 and, on the other
hand, the rays through the second optical system 24'. In the
embodiment of FIG. 4, as in that of FIG. 5, comprising a common
sensor 18 associated with the two optical systems 24, 24', the path
difference can be compensated for example by increasing the depth
of field, for example by means of a diaphragm, and/or by performing
a mid-focusing of the lens system 20, and/or by using an additional
dioptric or catoptric optical system interposed in either of the
two optical systems 24, 24'.
[0165] In the embodiment of FIG. 7A, a first common light source 28
illuminates a point T of the ring surface 16 by means of radial
incident light rays RI1 which are reflected into reflected rays RR1
for the first observation system whose first peripheral observation
field defines a first observation elevation angle .gamma.1 less
than 45 angle degrees, but greater than or equal to 25 angle
degrees, the reflected rays RR1 being, in the first area upstream
of the field-of-view of the common sensor 18, centripetal in their
course between the ring surface 16 and the installation axis A'1,
to reflect in a centrifugal manner on the first primary
frustoconical reflection surface 261 after having intersected the
axis A'1. In FIG. 7A always, a second distinct light source 28'
illuminates the same point T of the ring surface 16 by means of
second radial incident light rays RI2 which are reflected into
reflected rays RR2 for the second optical system 24' whose second
peripheral observation field defines a second observation elevation
angle .gamma.2 distinct from the first angle, here greater than 45
angle degrees, for example greater than 65 angle degrees, even
greater than 75 angle degrees, the reflected rays RR2 being, in the
second upstream portion of the field-of-view, centripetal towards
the installation axis A'1 in their course from the ring surface 16
in the direction of the second optical system 24' which is here
limited to the lens 20'.
[0166] In FIG. 7B, a common single light source 28, annular about
the installation axis A'1, illuminates the ring surface 16 by means
of the incident rays RI1, RI2 which are reflected, at the same
point T of the ring surface, respectively [0167] into reflected
rays RR1 according to the first peripheral observation field,
defined by the first optical system 24, and which here has a first
observation elevation angle .gamma.1 greater than 45.degree., the
reflected rays being in the first portion upstream of the
field-of-view, centrifugal in their course between the ring surface
16 and the first primary frustoconical reflection surface 261.
[0168] into reflected rays RR2 according to the second peripheral
observation field, defined by the second optical system 24, and
which here has a second observation elevation angle .gamma.2,
distinct from the first angle, here greater than 45.degree., for
example greater than 65 angle degrees, or even greater than 75
angle degrees, the reflected rays RR2 being, in the second upstream
portion of the field-of-view, centripetal towards the installation
axis A'1 in their course from the ring surface in the direction of
the second optical system 24' which is here limited to the lens
20'.
[0169] Note that, in the embodiments of FIGS. 7A and 7B, the two
optical systems 24, 24' are non-telecentric. Alternatively, either
or both of the two optical systems 24, 24' could be telecentric.
Likewise, although illustrated with a common sensor, variants may
be provided with distinct dedicated sensors.
[0170] It is therefore understood that all angle combinations are
possible for the torque formed by the first elevation angle and by
the second observation elevation angle, provided that these two
angles differ, preferably by at least 5 angle degrees.
[0171] In all cases, the first and second optical systems are
configured, relative to the associated sensor 18, 18', to determine
respectively a first upstream field-of-view portion CAM1 and a
second upstream field-of-view portion CAM2 which overlap, in the
installation area E according to a useful volume of inspection VUI
of revolution about the installation axis A'1. Thus, any point of
an object located in the useful inspection volume, which is
properly lighted, and which is imaged by a first image point in the
first image formed by the first optical system on the first sensor,
is also imaged by a second image point in the second image formed
by the second optical system on the second sensor. This useful
volume VUI, which forms a common inspection area, must have a
geometry adapted to be able to receive the ring surface 16 of a
container to be inspected. In the illustrated examples, this useful
volume has a shape generated by the revolution, about the
installation axis A'1, of a rhombus, this rhombus being possibly
truncated, for example in the embodiment of FIG. 1A, depending on
the depth of field determined by the optical systems 24, 24' for
the associated sensors.
[0172] For the embodiment of FIG. 1A, this property is highlighted
on the schematic graph in FIG. 1C. On this graph, the high and low
limits of the first upstream field-of-view portion CAM1 and the
high and low limits of the second upstream field-of-view portion
CAM2 are represented in dashed lines in section in one half of a
radial plane Pr. These two portions overlap according to the useful
inspection volume VUI.
[0173] In all the embodiments, these two upstream field-of-view
portions CAM1, CAM2 are each imaged, by the associated optical
system 24, 24', respectively on a first area and on a second image
forming area of the image sensor, said image forming areas of the
sensor associated respectively with a first and a second image area
of the overall image IG delivered in the sensor, this overall image
therefore being common for the two optical systems in the example
illustrated in FIG. 1D. This reasoning is made for the embodiments
including a single common sensor associated with the two optical
systems 24, 24'.
[0174] In the embodiments including two distinct dedicated sensors,
one for each optical system, as illustrated in FIG. 3, it will be
possible to ensure that a first overall image IG delivered by the
first sensor, and a second overall image IG' delivered by the
second sensor 18' includes in this way respectively a first image
of the ring surface 16, in a first image area of the first overall
image, and a second image of the ring surface 16, in a second image
area of the second overall image. In this case, it should also be
noted that it is possible to merge the two overall images, by
computer, to obtain a composite overall image identical or similar
to the common overall image obtained with a common sensor, provided
that they are represented disjoint.
[0175] In the embodiments including a single common sensor
associated with the two optical systems 24, 24', it will be noted
that the first image area ZI1 and the second image area ZI2 are
disjoint in the common overall digital image. The two optical
systems simultaneously form, on the same two-dimensional sensor 18,
two images separated in two distinct image-forming areas of the
sensor, such that the latter delivers an overall image comprising
two distinct image areas, each distinct image area including an
image of the ring surface from the rays collected according to the
peripheral observation field having the observation elevation angle
determined by the corresponding primary reflection surface. Thus,
this allows the simultaneous formation, from the reflected rays
collected according to the first and second peripheral observation
fields, via the optical systems 24, 24', of a two-dimensional image
I161, I162 of the ring surface of the container both in the first
image area ZI1 corresponding to the observation according to the
first peripheral observation field having the first observation
elevation angle .gamma.1 and in the second image area ZI2
corresponding to the observation according to the second peripheral
observation field having the second observation elevation angle
.gamma.2. In this case, there will be therefore, for each
container, an overall image including two image areas each
including an image of the ring surface, from two different
observation elevation angles. This common overall image IG is
preferably acquired during a single acquisition time of the image
sensor 18. In the case of two sensors, the two overall images can
advantageously be acquired simultaneously. However, it can on the
contrary be provided that the first ring surface image and the
second ring surface image are acquired at distinct times.
[0176] The images of the ring surface I161, I162 are formed by the
radial rays of the corresponding incident light beam which are
reflected by specular reflection on the ring surface 16 and
directed by the corresponding optical system 24, 24', on the
associated sensor 18, 18'. In some embodiments, it will be
considered that the image I161, I162 of the actual ring surface
consists only of these radial rays of the corresponding incident
light beam which are reflected by specular reflection on the ring
surface 16 and directed by the corresponding optical system 24,
24', on the associated sensor 18.
[0177] In some embodiments, in particular those including two
distinct dedicated sensors and two distinct light sources, with a
sensor and a light source dedicated for each optical system, as
illustrated in FIG. 3, it will be possible to ensure that each
overall image includes only an image of the ring surface. Indeed,
it can be provided a first light source 28 emitting in a first
range of wavelengths and a second light source 28' emitting in a
second range of wavelengths, distinct from the first range. In some
embodiments, two ranges of wavelengths which do not overlap will be
chosen. It is therefore sufficient, in the formation of the first
image and of the second image of the ring surface, to carry out a
chromatic filtering so that each image is formed with the reflected
rays derived from the corresponding light source. This chromatic
filtering can be carried out for example in the form of a chromatic
optical filter in the optical path through one or both of the
optical systems 24, 24'. In the embodiment of FIG. 3, including two
distinct sensors 18, 18' and a separation blade 21, it is possible
to provide that the separation blade is a dichroic blade. The
chromatic filtering can be carried out at the sensor(s), using
sensors operating in different chromatic ranges or using, in the
processing of the signal collected by the sensor, only part of the
collected light signal. In a system including a single common, for
example tri-chromic (Tri CCD or of the Bayer type), sensor, it is
for example possible to use only one chromatic channel for the
first image area and another chromatic channel for the second image
area. This can make it easier to identify the image of the ring
surface in the corresponding image. This in particular makes it
possible to at least partially compensate for any stray
reflections, including those due to the possible presence of the
two light sources within the device.
[0178] Advantageously, each of the two optical systems 24, 24'
allows the optical formation of a two-dimensional image I161, I162
of the complete and continuous ring surface at 360 angle degrees
about the theoretical central axis A1 of the ring surface 16 on the
associated sensor 18, 18'. This complete and continuous optical
image is formed on the associated sensor without digital
transformation, only by an optical method acting on the light. In
the illustrated examples, this complete and continuous optical
image of the ring surface is formed on the sensor by the optical
system 24, 24', without digital transformation.
[0179] FIG. 1D represents an example of a common overall image or
of a composite overall image obtained as described above. Through
each optical system 24, 24', two planar optical images I161, I162
of the actual ring surface 16 were thus obtained on the associated
sensor, by means of two optical geometric transformations which
each convert the ring surface 16 into a ring surface image I161,
I162. Preferably, for each of the optical geometric
transformations, the relative angular positioning of two points of
the ring surface about the theoretical central axis A1 is not
modified, in the sense that the respective images of two points of
the actual ring surface, separated by an angular deviation about
the theoretical central axis A1, are separated, in the image
obtained by the considered optical geometric transformation, by the
same angular deviation around the image of the theoretical central
axis. For each of the two optical transformations, it is considered
that the same transformation theoretically converts the theoretical
ring surface into a theoretical ring surface image I161t, I162t, in
the sense that the theoretical ring surface image is the image,
which would be formed by the transformation, of an actual ring
surface which would be coincident with the theoretical ring
surface.
[0180] In FIG. 1C, the trajectory of two observation rays has been
illustrated in solid line, respectively according to the first
observation elevation angle and according to the second observation
elevation angle, derived from the point Ti of the actual ring
surface, in the direction of the photoelectric sensor 18, passing
respectively through the first and the second primary reflection
surfaces.
[0181] FIG. 1D illustrates the overall image IG as received by the
sensor 18 through the two optical systems 24, 24'. The two actual
images of the same ring surface, formed respectively according to
the two observation elevation angles, therefore respectively via
the two primary reflection surfaces 261, 262, are here illustrated
each in the form of a image line I161, I162 which is the image,
formed by the corresponding optical system on the common sensor 18,
of the reflection of the corresponding incident beam on the ring
surface 16. The thickness of these two image lines according to the
radial direction in the overall image IG is determined for example
in particular by the planar, rounded, inverted V-shaped or
polygonal geometry of the profile of the ring surface in section in
a radial plane, by the extent of the light source in the same
radial plane, and by the angle of the light range delivered by this
source. In most cases, an image of the ring surface I161, I162 can
be assimilated to a line, otherwise it will be possible to define a
line representative of the image of the ring surface, for example
choosing an internal or external edge line or a mid-line of the
image of the ring surface as a representative line. Such a line can
also be determined by segmentation, by "skeletonization", by
looking for a particular point for each traveled ray starting from
the center, etc.
[0182] As illustrated in FIGS. 1C and 1D, it is considered here
that the corresponding point Tti of the theoretical ring surface
16t is the point of this theoretical surface which would have the
same angular coordinate as the considered point Ti of the actual
ring surface 16 in a system of cylindrical coordinates (Z, .rho.,
.THETA.) centered on the theoretical central axis A1. The position
difference between a considered point Ti of the actual ring surface
and a corresponding point Tti of the theoretical ring surface is
the combination of an actual height difference dZ, along the
direction of the theoretical central axis, and of an actual radial
difference d.rho., along the radial direction perpendicular to the
theoretical central axis A1.
[0183] The image points ITi1, ITi2 of the ring surface image of the
container are the images of the considered point Ti of the actual
ring surface through respectively the first and second optical
systems, due to the corresponding optical geometric
transformation.
[0184] In this FIG. 1D, two lines I161t, I162t have been added,
illustrating respectively the theoretical ring surface image
according to the two observation elevation angles. The
corresponding theoretical image points ITti1, ITti2 of the
theoretical images I161t, I162t of the ring surface 16t are the
images of the corresponding point Tti of the theoretical ring
surface through respectively the first and the second optical
system, due to the corresponding optical geometric
transformation.
[0185] A theoretical line I161t, I162t representative of the
theoretical ring surface image can be a predefined line, for
example a circle centered on the image of the installation axis
IA'1.
[0186] Alternatively, a theoretical line I161t, I162t
representative of the theoretical ring surface image can be deduced
from the image of the ring surface I161, I162, for example by
calculation within an image processing device, by estimating the
corresponding theoretical line I161t, I162t. Different methods are
possible to deduce this theoretical line, for example of the type
"best fit curve", Hough transform, correlation, search for the
largest inscribed circle, etc. In these methods it is possible to
take into account values of the diameter a priori of the ring.
Indeed, the theoretical line I161t, I162t in a perfect optical
system and for a container centered in the installation area E
(A1=A'1) is a circle. The diameter of the circle of a theoretical
ring image (theoretical line I161t, I162t) can be known a priori
from the image processing system, using adjustment or
initialization means, for example by learning, or by entering or
downloading a value. Therefore, to know the theoretical line I161t,
I162t, its center needs to be determined from the image of the ring
surface I161, I162. It is possible to generalize these methods with
more elaborate shapes of theoretical curves like ellipses, or other
parametric curves for non-centered containers, therefore if A1 is
offset from A'1.
[0187] The two digital image areas ZI1, ZI2, each containing
respectively one of the two images of the same ring surface are, in
the example illustrated, concentric annular areas which correspond
respectively to the two primary reflection surfaces 261, 262.
[0188] As illustrated in FIGS. 1C and 1D, at least one of the two
optical geometric transformations and, at least for the embodiments
of FIGS. 1A, 3, 4 and 5, in reality the two optical geometric
transformations, converts, except in special cases, a position
difference between a considered point Ti of the actual ring surface
and a corresponding point Tti of the theoretical ring surface, into
a radial image offset dR1i, dR2i. A radial image offset dR1i, dR2i,
in the overall image IG, IG', is the distance between, on the one
hand, the image point ITi1, ITi2 in the corresponding actual ring
surface image I161, I162 and, on the other hand, the corresponding
theoretical image point ITti1, ITti2 in the corresponding
theoretical ring surface image I161t, I162t.
[0189] In the example illustrated, the two actual ring surface
images I161, I162, illustrated in solid line, are substantially
coincident over the entire periphery with the corresponding
theoretical ring image I161t, I162t, which are illustrated in
broken line. It can be seen that, in the first image area ZI1, in
the angular sector corresponding to the point Ti of the ring
surface having a localized defect, the first actual ring surface
image I161 stands out from the first corresponding theoretical ring
image I161t, and has, in the image, a radial image offset dR1i
relative to this image. It is seen that the position difference
between the two points Ti and Tti is converted according to the
first optical geometric transformation, due to the optical system
124, into a radial image offset dR1i on the image seen by the
sensor.
[0190] In the illustrated example, for which the second observation
elevation angle .gamma.2 is also a grazing angle, it is seen that,
in the angular sector corresponding to the same point Ti of the
ring surface having a localized defect, the second actual ring
surface image I162 also stands out from the second corresponding
theoretical ring image I162t and has, in the image, a radial image
offset dR2i relative to this image. it is seen that, in this
hypothesis, the position difference is converted according to the
second optical geometric transformation, due to the optical system
124, into a second radial image offset dR2i on the image seen by
the sensor.
[0191] It is noted that, for the configurations in which the
reflected rays undergo the same number of reflections, or a number
of the same parity, in their path between the actual ring surface
and the sensor 18, the two radial image offsets dR1i and dR2i can
be measured, in the overall image IG delivered per sensor, on the
same ray derived from a central point of the image which
corresponds to the image IA'1 of the installation axis A'1.
[0192] Preferably, for at least the first of the two optical
geometric transformations, for example the one implemented through
the first reflection surface 261, it is observed, in the first
planar image area ZI1 collected by the first sensor 18, that the
radial image offset dR1i resulting from a unit actual height
difference dZi is greater than the radial image offset resulting
from an actual radial offset d.rho.i of the same dimension between
a considered point of the actual ring surface and a corresponding
point of the theoretical ring surface. In other words, preferably,
for at least the first of the two optical geometric
transformations, the influence of an actual height difference dZi
is greater than the influence of an actual radial difference
d.rho.i in the radial image offset obtained in the first optical
geometric transformation obtained by the first optical system 24.
Thus, a height offset of 1 mm of the actual ring surface relative
to the theoretical ring surface would result in a radial image
offset of axial origin, while a radial offset of 1 mm of the actual
ring surface relative to the theoretical ring surface would result
in another radial image offset, of radial origin, of lower
value.
[0193] In some embodiments of a device of the invention, such a
preponderance of the radial image offsets of axial origin is
ensured by the fact that the first observation elevation angle is
less than or equal to 45.degree. angle degrees, even more if it is
less than 25 angle degrees. However, in the embodiment of FIG. 7B,
such preponderance is not provided for any of the two geometric
transformations defined by the two optical systems 24, 24'. In the
illustrated exemplary embodiments including a first frustoconical
primary reflection surface 261 concave in a plane perpendicular to
the installation axis, this property, according to which the
influence of an actual height difference is greater than the
influence of an actual radial difference in the radial image offset
obtained in the optical geometric transformation, is ensured in
particular by the angle of the primary reflection surface 261 with
respect to the installation axis A1. More specifically, the apex
half-angle a1, characteristic of the primary reflection surface
261, determines the influence ratio, on the radial image offset,
between a height difference and a radial difference in the actual
surface relative to the theoretical ring surface.
[0194] In the embodiments illustrated, with a first concave primary
reflection surface 261 and a send-back reflection surface 132, the
more this apex half-angle a1 of the primary reflection surface 261
decreases as it approaches 0 angle degrees, the greater the
influence of the height difference on the radial image offset. Of
course, it will be preferably ensured that the apex of the cone
which carries the primary reflection surface is disposed upwards
relative to said surface, so that the optical element 122 which
carries the primary reflection surface 261, 262 can be arranged
above the ring surface 16, the sensor 18 thus seeing the ring
surface 16 from above through the optical system 24. In the
illustrated case where the send-back reflection surface 132 has an
angle of 45 angle degrees, this apex half-angle a1 is less than
12.5 angle degrees so that the influence of the actual height
difference is very much greater than the influence of an actual
radial offset in the radial image offset.
[0195] Preferably, for at least the first of the two peripheral
observation fields, the radial image offset corresponding to a unit
actual height difference is at least 2.14 times greater, and more
preferably at least 3 times greater than the radial image offset
corresponding to an actual radial offset of the same dimension
between said point of the actual ring surface and a corresponding
point of the theoretical ring surface. In this way, it is ensured
that, in the image obtained, a radial image offset is very largely
due to a height offset of the actual ring surface relative to the
theoretical ring surface rather than to a radial offset between
these two surfaces.
[0196] In the examples illustrated in FIGS. 1A to 5, the
observation elevation angle .gamma.1 defined by the first primary
reflection surface 261 is of 15 angle degrees, and the apex
half-angle a1 of the first primary reflection surface 261 is of 7.5
angle degrees. More generally, in the configuration of the device
of FIG. 1A, the first primary concave reflection surface 261 can be
a frustoconical surface of revolution, continuous at 360 angle
degrees about the installation axis A1, and having an apex
half-angle a1 equal to half of the observation elevation angle.
[0197] In the configuration of the device of FIG. 1A, the second
observation elevation angle .gamma.2 also is less than 45 angle
degrees, and even preferably less than 25 angle degrees, and is
therefore a grazing angle, as seen above. It appears that there is
also, in the second image I162 of the ring surface, a radial image
offset dR2 corresponding to a unit actual height difference greater
than the radial image offset corresponding to an actual radial
offset of the same dimension between said point of the actual ring
surface 16 and a corresponding point of the theoretical ring
surface 16t.
[0198] On the contrary, in the embodiments of FIGS. 4, 5, 7A and
7B, the second observation elevation angle .gamma.2 is not a
grazing angle, as seen above. It can be for example greater than 65
angle degrees, or even greater than 75 angle degrees. In this case,
a radial image offset is very largely due to an actual radial
offset d.rho. of the actual ring surface relative to the
theoretical ring surface rather than to a height offset between
these two surfaces. This radial image offset for the second image
is therefore mainly of radial origin.
[0199] For the embodiment of FIG. 3, the second observation
elevation angle .gamma.2 is of 90 angle degrees. In this case, a
radial image offset dR2 is only due to an actual radial offset
d.rho. of the actual ring surface relative to the theoretical ring
surface. A height offset dZi between these two surfaces is not
visible on the second ring surface image. In other words, in this
device of FIG. 3, a radial image offset dR2i measured in the second
ring surface image I162 directly gives a value representative of a
radial offset of the actual ring surface relative to the
theoretical ring surface along a direction perpendicular to the
installation axis.
[0200] Possible methods for processing an image and determining
measurements for the inspection of the containers are explained in
the following description. In order for the measurements made in
pixel or sub-pixel units in the images to be translated into
physical measurements relating to containers, in particular in
length units, the calculations take into account the optical and
geometric characteristics of the first and second optical systems
24, 24', including lens systems 20, 20', and sensors 18 and 18'
such as: the dimensions of the pixels, the focal lengths of the
lenses, the distances and positions of the optical elements and of
the ring surface, and the angles of the frustoconical mirrors, etc.
These optical and geometric characteristics are therefore
considered to be known to the image processing system. They are
made available to the image processing system either by any storage
medium, for example by input or by calibration of the device.
[0201] These optical and geometric characteristics are also used to
calculate geometric rays corresponding to optical rays in order to
perform any useful calculation in the three-dimensional measurement
space.
[0202] Thus, more generally, in the images which are obtained by
the method and/or the device described above, it is possible to
carry out, by image processing, the determination of points of
interest of each ring image. These determinations will be made for
a number N of analyzed directions Di, derived from a reference
point O of the overall digital image and angularly offset from each
other around the reference point O, which will be preferably the
image IA'1 of the installation axis.
[0203] It is noted that it is then possible to work in a common
overall digital image delivered in the case of a common sensor or,
in the case of two dedicated sensors, in a composite overall
digital image obtained by composition of the two overall digital
images delivered separately by two delivered dedicated sensors, or
separately in the two delivered overall digital images separately
by two dedicated sensors. In all cases, it will be ensured to take
account of any optical inversion between the two two-dimensional
digital images, any magnification difference between the two
images, any orientation difference, even if it means readjusting
the two images if necessary so that they are geometrically
comparable.
[0204] Thus, it will be possible to determine, according to the
analyzed direction Di, a first image point ITi1 of the first
two-dimensional digital image I161 of the ring surface 16, on the
analyzed direction. This image point ITi1 is the image of the point
Ti of the ring surface through the first optical system. It is then
possible to determine a first value representative of the distance
from this first image point to the reference point in the first
overall digital image IG. In the example mentioned above, this
representative value can be the value of the first radial image
offset dR1i, i.e. the distance between the first image point ITi1
and a first theoretical image point ITti1, belonging to the first
theoretical ring surface image I161t and located in the same
direction. This first radial image offset dR1i is therefore, in
this example, the distance, along the analyzed direction, derived
from the reference point, between the line I161 representative of
the first image of the ring surface 16 and the theoretical line
I161t representative of the theoretical ring surface image in the
first image. However, it is also possible to take, as a
representative value, the value of the distance from this first
image point to the reference point in the first overall digital
image IG as will be described later.
[0205] It is also possible to determine a second image point ITi2
of the second image I162 of the ring surface 16, on the same
analyzed direction Di derived from the reference point IA1, IA'1.
This image point ITi2 is the image of the same point Ti of the ring
surface through the second optical system 24'. It is then possible
to determine a value representative of the distance from this
second image point ITi2 to the reference point IA1, IA'1 in the
second overall digital image IG'. In the example mentioned above,
this representative value can be the value of the second radial
image offset dR2i, always for the same analyzed direction Di, i.e.
the distance between the second image point ITi2 and a second
theoretical image point ITti2, belonging to the second theoretical
ring surface image I162t and located in the same direction. This
second radial image offset dR2i is therefore, in this example, the
distance, according to the analyzed direction, derived from the
reference point IA1, IA'1, between the line I162 representative of
the second image of the ring surface 16 and the theoretical line
I162t representative of the theoretical ring surface image in the
second image. However, as will be seen with reference to FIG. 1E,
it is also possible to take, as a representative value, the value
of the distance from this second image point to the reference point
in the second overall digital image IG.
[0206] Of course, for the two images, values representative of the
same magnitude will be taken.
[0207] On this basis, it is then possible to deduce, for each
analyzed direction Di, by a geometric triangulation relation in the
radial plane Pri, at least one value representative of an axial
position, along the direction of the installation axis A'1, from
the point Ti of the actual ring surface 16 whose images by the
first and second optical systems 24, 24' are respectively the first
image point ITi1 and the second image point ITi2.
[0208] Referring to FIG. 1D, this geometric triangulation relation
uses for example: [0209] the first value, for example the first
radial image offset dR1i; [0210] the second value, for example the
second radial image offset dR2i; [0211] the first observation
elevation angle .gamma.1, and [0212] the second observation
elevation angle .gamma.2.
[0213] Indeed, by orthogonal projection in a radial plane Pri
containing the installation axis A'1 and passing through the
considered point Ti, therefore containing the analyzed direction
Di, it is possible to determine relations connecting: [0214] an
actual radial offset d.rho.i between the points Ti and Tti
considered in the radial plane Pri containing them; [0215] a height
difference dZi along the direction of the installation axis between
the considered points Ti and Tti [0216] the radial image offsets
dR1i and dR2i measured in the overall image.
[0217] In the exemplary embodiment illustrated, this relation can
be described by the equations:
dR1i=dZi*G1*cos(.gamma.1)+d.rho.i*G1*sin(.gamma.1)
dR2i=dZi*G2*cos(.gamma.2)+d.rho.i*G2*sin(.gamma.2)
[0218] where G1 and G2 are functions of the magnification
respectively of the first lens system 20 and of the second lens
system 20'.
[0219] Alternatively, with reference to FIG. 1E, it will be
possible to determine, according to the analyzed direction Di, a
first image point ITi1 of the first two-dimensional digital image
I161 of the ring surface 16, on the analyzed direction. This image
point ITi1 is the image of the point Ti of the ring surface through
the first optical system. It is then possible to determine the
distance R1i from this first image point to the reference point O,
for example the image IA'1 of the installation axis, in the first
overall digital image IG. This value can be called radial image
coordinate R1i.
[0220] It is also possible to determine a second image point ITi2
from the second image I162 of the ring surface 16, on the same
analyzed direction Di derived from the reference point O. This
image point ITi2 is the image of the same point Ti of the ring
surface through the second optical system 24'. It is then possible
to determine the distance R2i from this second image point ITi2 to
the reference point O in the second overall digital image IG'. This
value can be called radial image coordinate R2i.
[0221] On this basis, it is then possible to deduce, for each
analyzed direction Di, by a geometric triangulation relation in the
plane Pri, at least one value Zi representative of an axial
position, along the direction of the installation axis A'1, and a
value .rho.i representative of a radial position of the point Ti of
the actual ring surface 16 whose images by the first and the second
optical system 24, 24' are respectively the first image point ITi1
and the second image point ITi2.
[0222] This geometric triangulation relation uses for example:
[0223] the first value, the radial image coordinate R1i of the
first image point ITi1; [0224] the second value, the radial image
coordinate R2i of the first image point ITi2; [0225] the first
observation elevation angle .gamma.1, and [0226] the second
observation elevation angle .gamma.2.
[0227] Indeed, by orthogonal projection in a radial plane Pri
containing the installation axis A1 and passing through the
considered point Ti, therefore containing the analyzed direction
Di, it is possible to determine relations connecting: [0228] the
radial position .rho.i of the point Ti with respect to the
installation axis A'1 in the radial plane Pri containing them;
[0229] the axial position Zi along the direction of the
installation axis A'1 for the point Ti.
[0229] R1i=Zi*K11*cos(.gamma.1)+.rho.i*K12*sin(.gamma.1)+K13
R2i=Zi*K21*cos(.gamma.2)+.rho.i*K22*sin(.gamma.2)+K23 [0230]
wherein Kij are constants depending on the geometrical and optical
characteristics of the device, as described above.
[0231] For all directions Di, therefore for all the planes Pri
therefore for all the angles .theta.i, the complete cylindrical
coordinates of a point Ti of the ring surface are thus known.
[0232] An equivalent method is to calculate, in a given radial
plane Pri, for the image points IT1i and IT2i, the associated main
observation ray, and to consider the position of the point Ti as
being the intersection of the two main observation rays thus
calculated. Indeed, by knowing the optical and geometric
characteristics of the device, it is possible to associate with
each image point of an image, a main observation ray for this point
of the image. Thus, the two image points IT1i and IT2i
corresponding to the same actual point make it possible to
determine the equation of two main observation rays, therefore each
having a different observation elevation angle. Such a method
remains based on a geometric triangulation relation using a first
value representative of the distance from the first image point to
the reference point, a value representative of the distance from
the second image point to the reference point, the first
observation elevation angle .gamma.1, and the second observation
elevation angle .gamma.2.
[0233] According to a variant, one of the two images I161
(respectively I162) of the ring surface can be analyzed by
considering together the N image points IT1i (respectively IT2i) to
obtain an estimate of one of the two values, either of the actual
radial offset d.rho.i, or of the height difference dZi. For
example, from the N points IT2i of the second image I162, an
estimate, for each direction, of the actual radial offset d.rho.i,
is determined. This estimate of the actual radial offset d.rho.i is
then taken into account to correct estimates of height difference
dZi only from the points IT1i.
[0234] According to a variant, the second image I162 is obtained
with a device like those of FIG. 3 or 4, with a downward
observation elevation angle, in particular greater than 75 angle
degrees, in which the influence of the actual height difference
dZi, on the radial position of the second image point or on the
radial image offset dR2i, is insignificant or even zero if
.gamma.2=90 angle degrees. In this case, it is possible to first
analyze the second image I162 of the ring surface by considering
together the N points IT2i. From the N points IT2i of the second
image I162, values representative of the off-centering and/or of
the roundness are determined, for example the actual radial offset
values d.rho.i. In a second step, these values determining the
shape and position of the cylinder of the ring, it is possible to
determine with great accuracy the position dZi of each actual
object point Ti from the position of the image point IT1i.
[0235] Indeed, in general, it is considered that an actual radial
offset d.rho.i of a point Ti of the ring surface may be due: [0236]
a) to the off-centering of the theoretical central axis A1 of the
ring with respect to the axis A'1 of the installation during
shooting. [0237] b) to a defect in roundness.
[0238] The following explanation neglects the influence of a
possible inclination, which can however be taken into account
elsewhere.
[0239] In all cases, for the first image obtained after reflection
on a primary reflection surface, in the absence of any defect in
roundness but in the presence of an off-centering, the first actual
ring surface image I161 is a parametric curve, resulting from the
observation of a circle through its reflection on the frustoconical
mirrors. In the absence of off-centering, this first image is a
circle.
[0240] On the contrary, in the absence of any defect in roundness,
the actual ring surface image I162 is a circle centered or not for
the embodiment of FIG. 3 and an ellipse for the embodiment of FIG.
4. It is easy to determine a circle or an ellipse in the image area
ZI2 by means of known algorithms and therefore to know the
off-centering. It is possible to define therefrom a measurement in
the image frame in pixels or in the actual frame in millimeters of
the distance between the axes A1 and A'1.
[0241] For the embodiments of FIGS. 3 and 4, the defects in
roundness are then the deviations between the theoretical curves
and the actual curves. A defect in roundness is then determined for
example by looking for the second theoretical line I162t of the
circle or ellipse type most closely approaching the actual curve
I162. An algorithm similar to the previous one is therefore
applied. For the embodiments of FIGS. 3 and 4, the defects in
roundness are then the deviations between the theoretical curves
and the actual curves. It is possible to define therefrom, in the
image frame in pixels or in the actual frame in millimeters,
measurements, and compare these measurements with tolerance
thresholds. An example of measurement is given by the area surface
comprised between the two compared curves, or a distance value
between these curves. Other criteria are possible. These are in any
case values representative of the distance from image points to
reference point in the corresponding digital image.
[0242] In general, the method for analyzing the images IG, IG' by
the image processing system, for the determination of a
three-dimensional geometry of an actual ring surface of a
container, takes into account the optical and geometric
characteristics of the device. In the image IG, IG', a reference
point is selected as the origin O of an image frame of polar
coordinates. Preferably this origin is the point IA'1 which is the
image by the first system of the installation axis A1'. Each pixel
P of the image IG, IG', therefore has as polar coordinates
P(R,.theta.), its radius R defined as its distance to the reference
point and the angle .theta. of the radius PO.
[0243] It is noted that, for some methods, the more the observation
elevation angles .gamma.1 and .gamma.2 are different, the more the
calculation, in particular the triangulation calculation, will be
accurate. If the second observation is "vertical" or almost
vertical (.gamma.2 equal to or close to 90 angle degrees), it
"sees" no or almost no possible height difference dZi and therefore
allows a reliable calculation of the actual radial offset. The
complementary observation, obtained according to the first
observation elevation angle, will be able to evaluate the height
difference dZi with accuracy because it will be possible to
compensate by calculation any radial offset, in particular if the
first observation elevation angle .gamma.1 is less than or equal to
45.degree. angle degrees, and even more if it is less than
25.degree. angle degrees.
[0244] Thus, by repeating these calculations for a determined
number N of different directions Di, preferably distributed over
the 360 angle degrees around the reference point, it is possible to
determine the geometry of the actual ring surface and deduce
therefrom the presence of different defects of the ring surface, in
particular: [0245] unevenness, for example of the "dip" type, or of
the "saddle" type; [0246] defects in roundness; [0247] etc.
[0248] Preferably, for all the methods above, a sufficient number N
of directions Di will be taken to have, over the 360 angle degrees
of the ring surface, sufficiently fine geometric information for
the defects to be observed. Preferably, the number of directions Di
is chosen so that, over the 360 angle degrees, the two directions
Di are not separated by more than 20 angle degrees, preferably not
separated by more than 10 angle degrees, more preferably not
separated by more than 5 degrees apart. This will result
respectively in at least 18 distinct directions, preferably at
least 36 distinct directions, more preferably at least 72 distinct
directions.
[0249] It will be noted that the proposed device and method have
the advantage of being able to determine unevenness independently
of a possible defect in the roundness of the ring surface, for
example an ovalization and, more importantly, independently of a
possible defect in centering of the ring surface, defect which may
be a defect inherent in the geometry of the container (decentering
of the ring surface with respect to the theoretical central axis of
the container A1) or which may be a mispositioning of the container
in the installation at the time of the inspection (centering of the
ring surface with respect to the installation axis A'1). This last
point is important because it allows increasing the tolerances for
positioning the container during the inspection. This is very
significant for an online inspection, in particular at high
rate.
[0250] They also allow taking into account and measuring the
inclination defects of the ring.
[0251] In a method in which another representative value will be
determined, for example the value of the distance from this second
image point to the reference point in the first overall digital
image IG, there will be directly the coordinates of the
corresponding points of the ring surface in a cylindrical
frame.
[0252] In all cases, it is thus possible to determine information
representative of the three-dimensional geometry of the actual ring
surface 16 of the inspected container 14.
[0253] This determination can be made, in a device according to the
invention, by an image processing system associated with the sensor
18, including in particular for example a computer.
[0254] FIG. 6 illustrates an inspection line 200 of containers 14
implementing a device 10 according to the invention. In the example
illustrated, containers 14 are moved by a conveyor 210 which
transports the containers 14 along a direction of movement, for
example of horizontal translation perpendicular to the theoretical
central axis A1 of the containers 14. In the example illustrated,
the conveyor 210 includes a conveyor belt 212 on which the
containers 14 are laid by their bottom surface, also called a
laying plane, with their theoretical central axis A1 arranged
vertically. The conveyor 210 could also include guide means (not
represented) cooperating with the lateral faces of the containers
14. The conveyor 210 could also include opposite transport belts,
exerting a tightening of the lateral faces of the container for
their transportation over a linear portion. The conveyor could
include a conveying wheel moving the containers 14 along a circular
movement trajectory, in particular in a horizontal plane. The
containers 14 thus have their ring surface 16 in a horizontal plane
turned upwards. The conveyor 210 brings the containers along the
horizontal trajectory below the device 10 according to the
invention, without risk of interference with the device 10. The
device 10 can be carried by a support, for example in the form of a
casing 230, incorporating the device 10, in particular the
sensor(s) 18, 18', the lens systems 20, 20', the light source(s)
28, 28', the primary reflection surface(s) 261, 262. The casing 230
is arranged above the conveyor. Inside the casing 230, the device
10 according to the invention is arranged with its installation
axis A'1 in a vertical position, so that the observation fields and
the incident light beam are oriented downwards, towards the
installation area E which is located between the lower face of the
casing 230 and the conveyor belt 212. It is therefore understood
that, at this inspection station, the conveyor 210 brings the
containers so that their theoretical central axis A1 best coincides
with the installation axis A'1. At the time of this coincidence, at
least a first image and a second image are acquired using the
device 10, possibly in the form of a common overall digital image,
without this requiring handling the container or stopping the
conveyor. The images acquired by the device 10 can then be sent to
a processing device 240, for example an image processing system
and/or a viewing device and/or an image storage device, for example
a computer system comprising a computer. It is then possible to
analyze the images thus acquired and to determine the
three-dimensional geometry of the ring surface 16 of the container
14.
[0255] The camera can be triggered to integrate the images
synchronously with the movement of the articles, in particular to
freeze the image when aligning the theoretical ring central axis A1
with the installation axis A'1. The integration time is expected to
be short, for example less than 1 ms, or even less than 400 .mu.s,
in order to reduce the risk of camera shake in the images.
[0256] The light source can be pulsed, that is to say produce the
lighting for a short period of the flash type, for example less
than ims, or even less than 400 .mu.m, in order to reduce the
camera shake in the images.
[0257] It can be provided that the processing system 240 cooperates
with, or includes, a control unit, which drives the light source
and the camera, in order to synchronize them with the movement of
the articles.
[0258] The device and the method are therefore without physical
contact with the container to be controlled. A device according to
the invention proves to be less costly and of smaller bulk than
devices of the prior art, in particular allowing its easy
installation in a station or on an article inspection line,
inspection station or line which may include other devices intended
for other controls, and the device according to the invention can
thus be installed in particular in a production line where the
containers circulate like a chain. Such a device then allows the
control of containers online, whether on a container production
line, or on a container processing line, or on a filling line, at
high rate.
[0259] The invention is not limited to the examples described and
represented since various modifications can be made thereto without
departing from its scope.
* * * * *